m900 cant shake off the cold

[stef]

my m900 has been sick for almost a year now, and since i have changed most things on the bike and still cannot find the problem, i thought i'd pick the forum's comunity brains.

i'll try to describe the symptoms the best i can:
The bike starts okish, usually, as it can be expected from a monster. idle is good, noise is as expected, regular, and strong.
acceleration is very good, nothing unexpected from the setup. Decceleration is also good, engine wizzes down without glitches.

It's crusing around that's a little more tricky...
whether it's at 20mph, 30mph or 60mph, the engine does not behave the way it should. it misses explosions once in a while (like 2-3 times a second)
resulting in a very very annoying ride. if it's very unconfortable at 60, it's a right pain around round abouts and frankly dangerous when filtering through traffic. that's because the bike is fine when accelerating, therefore, i just keep on acelerating whenever a bit of road requires me to be confortable in my boots and stop shaking all over... but accelerating is also a little dangerous when filtering...

instead of the steady, throaty engine purr which sould sound like beeeeeeeeuuuuuuuuurrrrrrrrrrrrrrrrrr..., i get a beeubeuubebebeuuuuuuurrrbeuuuubeuuu... (with a french accent)

now for the things i tried:

-i started playing around with the carbs: adjusted the mixture, synching, floats.that did not work. i then changed the mikunis for FCRs, as you do.
i got the FCR's (39) out of the box, and plugged them in, no tweaking (they were previously installed on a m900.) results: not much different, altough maybe a little better (but it's hard to say, since it had been a while since i'd ridden the sick monster. pulling was much better though, as it should be expected from FCRs! i have pod filters on the air intake.

-electrics:
I changed the coil, and i changed the ignition modules. no difference whatsover. I also changed the spark plugs and connecting wires.

-engine:
i checked and adjusted the valve clearances. they were a bit off, especially on the closers (0.1mm). they are now much tighter. still no obvious cure to the problem. I had a bit of a mishap when checking the valves (dropped the half moon down the engine) so i had to take the engine apart (top end). i didnt see anything obvious. I also changed the inlet gaskets.
I changed the fuel filter, and removed anything questionable on the fuel line (quick release connector).

I am now running short of ideas.. anyone ?

[utopia]

That's a bit of a puzzler.
It does sound kinda like its a fuelling issue to me, but its strange that fitting the FCRs had no effect at all.
Clutching at straws somewhat.....do you have the vacuum operated fuel pump and/or fuel tap ? I'm wondering if the vacuum is insufficient at cruising throttle openings but just adequate at wider throttle openings....ie there is a vacuum leak somewhere....?

The problem sounds too predictable for it to be an intermittent/random wiring issue, and you've changed much of the ignition system anyway so most of the components have been verified.
Another long shot, but could there be an issue with the flywheel pick-ups for the cdi units ? I have heard of flywheel nuts coming loose. Maybe something like this could cause a difference between cruising and accelerating modes as the flywheel shifts position slightly under different crank inertia conditions. I guess a worn woodruff key (if there is one in there) could also be involved.

I'm not too sure about either of these suggestions, but its all I can think of so far and I thought I might as well mention them for you to ponder further.

[stef]

That's a bit of a puzzler.
It does sound kinda like its a fuelling issue to me, but its strange that fitting the FCRs had no effect at all.
Clutching at straws somewhat.....do you have the vacuum operated fuel pump and/or fuel tap ? I'm wondering if the vacuum is insufficient at cruising throttle openings but just adequate at wider throttle openings....ie there is a vacuum leak somewhere....?

The problem sounds too predictable for it to be an intermittent/random wiring issue, and you've changed much of the ignition system anyway so most of the components have been verified.
Another long shot, but could there be an issue with the flywheel pick-ups for the cdi units ? I have heard of flywheel nuts coming loose. Maybe something like this could cause a difference between cruising and accelerating modes as the flywheel shifts position slightly under different crank inertia conditions. I guess a worn woodruff key (if there is one in there) could also be involved.

I'm not too sure about either of these suggestions, but its all I can think of so far and I thought I might as well mention them for you to ponder further.

well, thank you for that.
i was chatting away at lunch time, and the fuel pump also came up in the conversation ....as you said, a vaccum leak would explain it.

i dont fancy the second option..

and fitting the FCRs did have an effect, i seem to remember, but it did not fix the issue.
I have a spare fuel pump.. i might try swapping it.

[Pomp1]

Is petrol flowing ok from the tank to the first pump? Are the pipes connected nicely all around the vacuum system? Are the nipples screwed in properly in the inlets? My money is on fuel rather than electric as the pickups would have finally gave up the host by now.
Try to go for a quick blast with the petrol cap open and see if it helps.

[stef]

Is petrol flowing ok from the tank to the first pump? Are the pipes connected nicely all around the vacuum system? Are the nipples screwed in properly in the inlets? My money is on fuel rather than electric as the pickups would have finally gave up the host by now.
Try to go for a quick blast with the petrol cap open and see if it helps.

after drenching the bike in petrol yesterday, i can confirm that there is no blockage from the tank to the first...thinggy.
what's that thinggy, btw ? it's attached just below the tank hinge, and, as the fuel pump, it also receives a vaccum tube.
I always thought it was a vaccum operated fuel tap.. is that so ?
i guess it is safe to bypass it..
I'll try that too, along with the petrol cap open.

[Ducmon]

I was getting sttrange things happening to mine where it woukld miss for a few seconds. This got steadoly worse inttermittily running on one cyclinder but never the same one. I eventually traced it down to the pickups breaking down under temperature.

[utopia]

what's that thinggy, btw ? it's attached just below the tank hinge, and, as the fuel pump, it also receives a vaccum tube.
I always thought it was a vaccum operated fuel tap.. is that so ?


Yes, I think it is.
You could probably bypass it if you still had the original carbs, but I seem to remember Saint saying that with FCRs, it will just cause the tank to dump all its fuel into the engine.....!!!!..??? ......Dunno myself, just passing it on.
If you do bypass it, it might be worth clamping the fuel line while the engine isn't running, or else fit a manual tap, just to be sure.

[Kato]

Stef as mentioned already by Ducmon my money is on the pick-ups or one of the pair at least, you can test them with an ohm meter should be 220 ohms + or - 5%

[stef]

Stef as mentioned already by Ducmon my money is on the pick-ups or one of the pair at least, you can test them with an ohm meter should be 220 ohms + or - 5%

Well,
I have changed the fuel pump tonight, and bypassed the vacuum tap.
and...
probably worse, to be honest.
here is were subjectivity comes in, but it fell worse. i really had to wack the throttle opened to get in the quiet zone. lightly picking up speed wouldnt do.
however, it could be a case of very bad luck with two petrol pumps. the one i fitted tonight was fine up to 2008, when i took it off my old monster. it has not been used since..so.. could be a little dry, i guess...
oh, and i tried cap opened. no difference.

now, those pickups..

[utopia]

Well I think that verifies your existing vacuum tap, and its vacuum pipe, but I'm not so sure about the pump.
I don't speak from much experience of them, but one that's been dry for 4yrs could well be suspect, as you say.
Perhaps even the fact that it was worse (probably) might suggest.... 1) that it is dodgy, and 2) that a dodgy pump causes your symptoms, ie the first one is dodgy too....????
Or maybe I'm thinking about this too much....
Anyway, did you also check the vacuum pipe to the pump for chafings, splits, leaky connections, ...collapsing under vacuum even....?

The pick-ups may well be suspect I guess, but I can't quite reason it through with your particular symptoms. (other than the loose flywheel thing, which surely would have worsened rapidly, rather than limped for nearly a year...??)

So, I was wondering......if it is the fuel pump (or its vacuum pipes), but its ok under acceleration, you would expect the float bowls to be full as you subsequently began to close the throttle, and so you might expect that the spluttering under cruising throttle conditions would not set in immediately, but only after some shortish period of cruising to allow the pump to lag behind, as it were.....???
Does that ring any bells ?

Also, if it starts (sort of) fine (eventually), that may point to the pump being unable to refill the float bowls until the engine's been cranked a few extra times.....?


Could be pick-ups though.
As you know, electrics are not my best subject.

[Saint aka ML]

No one mentioned timing? If timing is off it will misfire and more so under load so might appear fine under idle. Air gap of pickup sensors is also something to look at? What colour are the plugs? My one is overfueled lots down low and after start up if you set off asap it is jerky for 20s like what you describe. However I would start with easy stuff as Kato said test pickups, then report here also check plug colour and report. Should be chocolate brown. Black sod to rich, white crisp to lean.

[stef]

well, wrong conclusion on the pump. I realised this morning (just as i got out of bed, funny that) that i did not shut off the vaccum tube going to the fuel tap. The tube is still untouched and connects to the tap, but there are no fuel hoses connected.

so i guess the tap cannot be ruled out just yet.

I checked the pickups this morning, using a ohmeter on the pair of wires connected to the CDIs... both read 100ohms.
i'll check the specs today, unless someone has the definite value ?
regarding timing, i swapped the standard black CDIs for the performance, red ones.
that did not make a difference.

regarding the plugs, i checked them regularly, and they've usually been on the black side.
I just changed the valve stem seals, so i expect them to be a little less oily, maybe.
i'll recheck them tonight though.

[gary tompkins]

Stef as mentioned already by Ducmon my money is on the pick-ups or one of the pair at least, you can test them with an ohm meter should be 220 ohms + or - 5%

I checked the pickups this morning, using a ohmeter on the pair of wires connected to the CDIs... both read 100ohms.
i'll check the specs today, unless someone has the definite value ?
regarding timing, i swapped the standard black CDIs for the performance, red ones.
that did not make a difference.

See above... looks like both of yours could be faulty

[stef]

See above... looks like both of yours could be faulty

yep, i had your 220 figure in mind when checking them, but since they were both spot on 100ohms, i held on a minute before any celebration.
are you definitely sure it is 220 ?

[stef]

Anyway, did you also check the vacuum pipe to the pump for chafings, splits, leaky connections, ...collapsing under vacuum even....?

The pick-ups may well be suspect I guess, but I can't quite reason it through with your particular symptoms. (other than the loose flywheel thing, which surely would have worsened rapidly, rather than limped for nearly a year...??)

So, I was wondering......if it is the fuel pump (or its vacuum pipes), but its ok under acceleration, you would expect the float bowls to be full as you subsequently began to close the throttle, and so you might expect that the spluttering under cruising throttle conditions would not set in immediately, but only after some shortish period of cruising to allow the pump to lag behind, as it were.....???
Does that ring any bells ?

Also, if it starts (sort of) fine (eventually), that may point to the pump being unable to refill the float bowls until the engine's been cranked a few extra times.....?


Could be pick-ups though.
As you know, electrics are not my best subject.

starting is not really an issue, it will usually start at first engine rotation.
sorry, the shortish period of cruising is not really ringing any bells..it usually starts playing up right away.

regarding the timing, this may not anything to do with the current issue, but i noticed that the engine had a funny way of farting at me as soon as i turned the key off the ignition. after stopping the engine, key in the on position (to check the neutral), i turn the key to off, and puffff.. it farts.
not loud, not smelly, just a little pinched fart. The engine probably turns a smidge too, as a result.
like some tiny explosion of remaining mixture. but why at this particular instant, and why havent i noticed it before?

[don_matese]

Haynes manual says the pickups should be 95-105ohms and an airgap of 0.6 to 0.8mm

[utopia]

The official Ducati manual for my 750 confirms .....95 to 105 ohms.

[stef]

ok...thank you very much.
maybe a leak on the tap is still possible then.

[utopia]

I'd suspect the pump at least as much, if not more than the tap.
I haven't done this, but I'm wondering if you could do some sort of test on the tap by disconnecting the outlet pipe and the vacuum pipe, then sucking on the latter and seeing if fuel flowed from the outlet...?
....trying to avoid sucking the wrong pipe.
And re. the pump....I believe its possible to get repair kits.....Ducmon posted some time ago....Allen's Performance if memory serves.
Of course, the pickups could still be at fault mechanically, despite their resistance being ok......air gap ? ......or even the dreaded flywheel nut.

[stef]

I'd suspect the pump at least as much, if not more than the tap.
I haven't done this, but I'm wondering if you could do some sort of test on the tap by disconnecting the outlet pipe and the vacuum pipe, then sucking on the latter and seeing if fuel flowed from the outlet...?
....trying to avoid sucking the wrong pipe.
And re. the pump....I believe its possible to get repair kits.....Ducmon posted some time ago....Allen's Performance if memory serves.
Of course, the pickups could still be at fault mechanically, despite their resistance being ok......air gap ? ......or even the dreaded flywheel nut.

ok, thanks..
the tap is already bypassed (no issues with the Keihins, has far as i can tell)
just the vaccum hose is still connected.

Is there a quick way to check for the flywheel nut ?
or is it inevitably the left cover off ? (i've just replaced the oil !)

[Ducmon]

I used REPAIR KIT: MK-DF62 from allens performance, but your symtoms do sound very similar to mine. It took me two years to find the answer because it was only happening occasionally. I had luck by when it happened the last time that I had an ohms meter with me and found that the restancs where totally wrong. Half an hour later they were reading 100 ohms once again and the engine was running correctly.

I had cleaned fuel tank, replaced coils and cdi, repaired fuel pump, new spark plugs3 times and cleaned reset the carbs only to find that it was a 30 pound piece. Since I replaced the pick coils I have had no problems and she even starts better.

http://www.electrexworld.co.uk/acatalog/P8.html was the cheapest that I found.

[utopia]

I can't think of any way of checking the flywheel nut without the case coming off (unless maybe you can spot anything obviously amiss after taking off the little plate in the centre).
But I don't think its a particularly likely cause (sorry if I've caused concern).....it just seemed like one theoretical way to account for the symptoms, and like I said, I think it has been known to happen before... (quite probably I read about it in a thread on this forum).
If you do decide to change the pick-ups though, and therefore the case has to come off anyway, it might be worth checking before you actually order the new pick-ups.

[stef]

I used REPAIR KIT: MK-DF62 from allens performance, but your symtoms do sound very similar to mine. It took me two years to find the answer because it was only happening occasionally. I had luck by when it happened the last time that I had an ohms meter with me and found that the restancs where totally wrong. Half an hour later they were reading 100 ohms once again and the engine was running correctly.

I had cleaned fuel tank, replaced coils and cdi, repaired fuel pump, new spark plugs3 times and cleaned reset the carbs only to find that it was a 30 pound piece. Since I replaced the pick coils I have had no problems and she even starts better.

http://www.electrexworld.co.uk/acatalog/P8.html was the cheapest that I found.

mine is never working properly, yet, the coils read fine. Did yours eventually read an incorrect value ? or did you change them just as a test ?

[revver]

I've had the same symptoms as you on my 95 m600 for a year now, so will be interested to see what you find.

[Quantox]

Sounds like clogged up idle jets to me. Has the bike been standing for a while? If so, have you had a look inside the carbs, to see what crap the evaporated fuel has left behind?

Cheers

Q

[stef]

Sounds like clogged up idle jets to me. Has the bike been standing for a while? If so, have you had a look inside the carbs, to see what crap the evaporated fuel has left behind?

Cheers

Q

yes, it sounds like that, but if you read the first post, you can see the carbs have been replaced without making any difference.

[Ducmon]

mine is never working properly, yet, the coils read fine. Did yours eventually read an incorrect value ? or did you change them just as a test ?

Yes they did but I had checked them about 10 times and always got a correct reading. That is why I started carring an ohms meter with me to check them when it happened.

The way it started was the bike would start and when I started to pull away it would start poping and banging. I would then clean the spark plugs and it would run ok. Until it did it again.

Once it had got really bad it would start to run on one cylinder and then it would cut back in again.

I found that the air gap was ok and everything appeared ok when I checked them after I had removed the pick up coils I still get a reading of 100 ohms even now but it was deffiently where the problem lay.

[stef]

been looking at the wiring tonight. and something puzzles me:
i have on the bike, 4 wires from the pickups: a red/white pair, and a black/yellow pair.
so far so good.
first of all, could i swap red for white and yellow for black ?
i reckon a pickup coil is bidirectional, but is that true ? (and could mine be wired the wrong way round ?
looking at the bike, sitting on it, with the connectors of the CDIs up, i have red/white then yellow/black.
(in other words, red and yellow on the side of the three pin connector on each CDI)
red/white are on the horizontal.

that's that.

now i also have a discrepency between my bike, and the Haynes manual.
on Haynes, the grey wire from the CDI goes to the coil feeding the vertical plug. mine goes to the horizontal.
and of course, the green/brown is also inverted.

I think there is something in this, because the setup is not completely symetrical. the brown wire goes from the middle pin on the vertical CDI to the ignition switch and to a side pin on the horizontal CDI.
on my bike, i presume the brown wire is red, but it goes from the side pin on the veritcal to the side pin on the horizontal.

The haynes manual diagram is obviously wrong, but could i have wired my pickups/coils and CDI in some funky way ?

On another subject, i have checked the plugs, they are both on the black side.. same shade of black, which does look to me like both cylinders are behaving in the same way. this somehow does not go in the sence of the dodgy pickups theory, as it would be a very strange coincidence to have both coils messing about in that twisted sort of way.

[bikerjude]

I had a similar problem with my M900. It's a later injected model, but mine was due to a corroded tank which had clogged the filter. Might be worth checking inside and changing the fuel filter. Changed the filter which made it a bit better, then changed the fuel pump itself and now it's perfect. We were looking around for a 2nd hand tank, but before we could find one, I crashed the bike and damaged the tank, so got a brand new one on insurance!

[stef]

I had a similar problem with my M900. It's a later injected model, but mine was due to a corroded tank which had clogged the filter. Might be worth checking inside and changing the fuel filter. Changed the filter which made it a bit better, then changed the fuel pump itself and now it's perfect. We were looking around for a 2nd hand tank, but before we could find one, I crashed the bike and damaged the tank, so got a brand new one on insurance!

i changed the filter last sunday, and the pump a couple of days ago, no difference !
that's the thing with the monster.. so simple that the same symptoms could come from a thousand problems !

then again, crashing the bike to get a new one might just be the solution !

[utopia]

......then again, crashing the bike to get a new one might just be the solution !

Or maybe I could arrange for it to be stolen for you.
Hmmm....FCRs, you say........:devil:

But seriously.....
What year is the bike ? .....I'm not doing wiring spaghetti without some sort of diagram to look at, however inaccurate it might be.

Without wanting to flog a dead horse, I'm still not convinced that the fuel pump has been eliminated from suspicion.
I appreciate the subjectivity thing, but if it actually was slightly worse with the replacement pump, but similar, that might point to two duff pumps. I wonder whether it would seem to be slightly better, but similar, if you refitted the old pump again. ....?
You did also say that it was perhaps slightly better after fitting the FCRs, which might suggest that its a fuelling issue which is not directly caused by the carbs themselves, but has an effect on their operation......??

I'm also wondering whether there's anything to be learned from checking the ign timing (if you have, or can borrow a strobe). This may perhaps give further indication as to the performance of the pick-ups, or even the tightness of the flywheel nut.

As for the farty noise, that's a strange one and I'm tempted to just ignore it simply because its peculiar.....which would probably be a silly thing to do.
But I can't think of anything that would be triggered by switching off at the key (on a carby bike with vacuum fuel pump and no electronics) apart from maybe a relay, or an alarm/immobiliser if you have one fitted.

Hope that helps, though I'm not particularly convinced that it will.

[stef]

Or maybe I could arrange for it to be stolen for you.
Hmmm....FCRs, you say........:devil:

But seriously.....
What year is the bike ? .....I'm not doing wiring spaghetti without some sort of diagram to look at, however inaccurate it might be.

Without wanting to flog a dead horse, I'm still not convinced that the fuel pump has been eliminated from suspicion.
I appreciate the subjectivity thing, but if it actually was slightly worse with the replacement pump, but similar, that might point to two duff pumps. I wonder whether it would seem to be slightly better, but similar, if you refitted the old pump again. ....?
You did also say that it was perhaps slightly better after fitting the FCRs, which might suggest that its a fuelling issue which is not directly caused by the carbs themselves, but has an effect on their operation......??

I'm also wondering whether there's anything to be learned from checking the ign timing (if you have, or can borrow a strobe). This may perhaps give further indication as to the performance of the pick-ups, or even the tightness of the flywheel nut.

As for the farty noise, that's a strange one and I'm tempted to just ignore it simply because its peculiar.....which would probably be a silly thing to do.
But I can't think of anything that would be triggered by switching off at the key (on a carby bike with vacuum fuel pump and no electronics) apart from maybe a relay, or an alarm/immobiliser if you have one fitted.

Hope that helps, though I'm not particularly convinced that it will.

no, it doesnt !
but thanks anyway, and I agree completely with you re: the pump and the FCRs.
RE: the fart, i think there may be something there, because there is some electronics in the bike, in the CDIs. and one of the wires (the brown) goes to the ignition switch. I there was a spike in there (usually, you get a current spike when you violently change the voltage on a capacitor, or you get a voltage spike when you change the current inside a coil... you dont need anything too fancy to get that spike, if there is sufficent energy left in the coil and the CDI triggers it, i'll get a weakish spark on the plug, and the bike will fart.
question is, can you wire the bike in a weird way such that this happens.
bike is a 98. I'll try to swap the pump again this weekend.

[stef]

Not much to report, I havent had the time to work much on the problem. I only completely removed the vaccum tap from the fuel line, and plugged the vaccum intake from the inlet pipe.

I went for a quick ride tonight, and i have two observations:
the bike was fine at first (i even thought i'd sorted out the problem), but it started playing up again after 2-3 mins. It's downhill from there, but not worse than with the other pump.
I couldnt confirm that, after accelrating, it takes a few seconds to get bad. I just seems to get different degrees of bad depending on the speed i am doing.
It's worse between 20 and 35mph, the bike feels unrideable(round about speed !) and it's noticeable at 60.
however, I though of the following test:
get the bike warm and diconnect each plug in turn. the bike will have no power on just one cylinder, but i will be able to tell if it's cutting like it does on two. that will hopefully tell me if one cylinder is bad, or if it is both.

[Saint aka ML]

Stef do not remember which pickup goes to which coil and can not help as I have custom ignition. However can confirm that bike will do what you described if pickup plugs are witched or even wires on one of the pickups are switched. Had that mistake.
Issue there is that your colour of pickup wires can be different to others. What you would need to establish is which pair is first pickup (with direction of engine travel) and which second. Than compare it to another bike. If your colours are the same as some other monsters just ask for photos.
If someone was changing pickups they probably removed the plug on each pair of wires to get it through the hole in the case and could possibly put it back wrong.

In regards of coils to cylinder. Looking as you sit on the bike left coil goes to front cylinder.

[Saint aka ML]

Regarding your idea of running on one cylinder. Get it to do the issue described but then stop. Remove the plug cable and plug. Otherwise you will have plenty of petrol collecting in cylinder with no plug which can be bad if done for to long. Also it will be easier to start and run on one. Make sure the plug cable is no where near the petrol that is being pushed out ;D

[Quantox]

yes, it sounds like that, but if you read the first post, you can see the carbs have been replaced without making any difference.

Yes, you're correct. I did read the first post but then forgot about it as I read all the rest. Must do better next time.

Cheers

Q

[stef]

Stef do not remember which pickup goes to which coil and can not help as I have custom ignition. However can confirm that bike will do what you described if pickup plugs are witched or even wires on one of the pickups are switched. Had that mistake.
Issue there is that your colour of pickup wires can be different to others. What you would need to establish is which pair is first pickup (with direction of engine travel) and which second. Than compare it to another bike. If your colours are the same as some other monsters just ask for photos.
If someone was changing pickups they probably removed the plug on each pair of wires to get it through the hole in the case and could possibly put it back wrong.

In regards of coils to cylinder. Looking as you sit on the bike left coil goes to front cylinder.

I am starting to suspect that the wires are switched somehow !

[Mr Gremlin]

but if both sets have the wrong size pilot jet for your engine configeration it will still run sh1te on part throttle. :twak:


there was supposed to be a quote here LOL

[stef]

but if both sets have the wrong size pilot jet for your engine configeration it will still run sh1te on part throttle. :twak:


there was supposed to be a quote here LOL

symptoms appear on a healthy set of carbs (original mikunis) and remained on a new set of FCRs. the probability that it's related to the pilot jet is very remote ( i also thought it was the pilot circuit at first, so i changed the relevant orings and checked the cabs.. before swapping them for FCRs.)

to me, this could be the key:the CDIs ar ewired with 2 and 3 pins connectors, the sensors are on the 2 pins. can someone check that the
red and yellow wires (from the sensors ) are on the side of the three pin connector on each CDI ?
i found a picture confirming that the red sensor cable is indeed on the side of the 3 pins connector, but i couldnt find a picture showing the other side.


re: swapping the sensors round altogether (vert on horizontal), i doubt the bike would even start !
however, the sensors are not symetrical so swaping the terminals may be the solution, as Saint also suggests.

[Saint aka ML]

Depending from your timing setup swapping sensor plugs around (not wires) could make the bike start. My one was starting, just but at touch of throttle it was dead. Do not know if connecting wires from cdi to coil wrong way around would have similar effect or even connecting wrong cdi unit to coil?

[utopia]

On my yr2000 M750, the wiring to the cdi units is as follows.....

Reading from left to right (as viewed from sitting on the bike), my wiring goes.....
white. red. (2pin conn) black. green/brown. red (3pin) for the horizontal cyl ......then black. yellow (2pin) black. grey. red. (3pin).
ie. for the horiz. cyl. the red wire in the 2pin conn is nearest to the 3pin conn.
and for the vert. cyl. the yellow wire in the 2pin conn is nearest the 3pin conn.

Is that the info you need ?
And does it (as I think it might) suggest that yours is wired correctly ? (its hard to judge from written word...sorry I can't post a pic).

[Mr Gremlin]

symptoms appear on a healthy set of carbs (original mikunis) and remained on a new set of FCRs. the probability that it's related to the pilot jet is very remote ( i also thought it was the pilot circuit at first, so i changed the relevant orings and checked the cabs.. before swapping them for FCRs.)

to me, this could be the key:the CDIs ar ewired with 2 and 3 pins connectors, the sensors are on the 2 pins. can someone check that the
red and yellow wires (from the sensors ) are on the side of the three pin connector on each CDI ?
i found a picture confirming that the red sensor cable is indeed on the side of the 3 pins connector, but i couldnt find a picture showing the other side.


re: swapping the sensors round altogether (vert on horizontal), i doubt the bike would even start !
however, the sensors are not symetrical so swaping the terminals may be the solution, as Saint also suggests.

so, if ive got this right, your bike starts, runs, accelerates well, flies at full throttle, its just cruising on part throttle theres an issue ?? what relavent o-rings are there on a pilot jet ?

[stef]

so, if ive got this right, your bike starts, runs, accelerates well, flies at full throttle, its just cruising on part throttle theres an issue ?? what relavent o-rings are there on a pilot jet ?

if you unscrew completely the mixture screw (on the mikunis), you'll get a small needle out (from memory) a tiny spring and a oring. i beleive this is part of your pilot circuit.
This oring can sometimes leak, and cause the symptoms you described (which are what i am observing).
but in my case, the pilot circuit is not responsible.

[stef]

On my yr2000 M750, the wiring to the cdi units is as follows.....

Reading from left to right (as viewed from sitting on the bike), my wiring goes.....
white. red. (2pin conn) black. green/brown. red (3pin) for the horizontal cyl ......then black. yellow (2pin) black. grey. red. (3pin).
ie. for the horiz. cyl. the red wire in the 2pin conn is nearest to the 3pin conn.
and for the vert. cyl. the yellow wire in the 2pin conn is nearest the 3pin conn.

Is that the info you need ?
And does it (as I think it might) suggest that yours is wired correctly ? (its hard to judge from written word...sorry I can't post a pic).

thanks.
That's exactely what i was looking for. and it is in fact the exact way my bike is wired. I swapped the black and yellow, and the bike was way worse. popped and farted for 50 meters and then that cylinder just stopped firing.

I alss tried the running on one cylinder test yesterday. seems fine on horizontal. but i couldnt even start on the vertical. to be confirm with another test run and a fully charged battery !

[Mr Gremlin]

if you unscrew completely the mixture screw (on the mikunis), you'll get a small needle out (from memory) a tiny spring and a oring. i beleive this is part of your pilot circuit.
This oring can sometimes leak, and cause the symptoms you described (which are what i am observing).
but in my case, the pilot circuit is not responsible.

that is the mix screw not the pilot jet.
i am trying to help you here, but it looks like you would rather dismiss the advice from an experienced dyno operator and run your self around in circles.

Sooo, good luck .

[stef]

that is the mix screw not the pilot jet.
i am trying to help you here, but it looks like you would rather dismiss the advice from an experienced dyno operator and run your self around in circles.

Sooo, good luck .

dont get your knickers in a twist, i dont mean to just brush off your advice, it's just that i too first suspected the pilot circuit (which is just underneath the mixture screw: see Fig 2. http://www.iwt.com.au/mikunicarb.htm (first link that came up in google) The mixture screw adjusts in the pilot jet. and there is an O'ring around that screw...if leaky, you get the wrong mixture, but i am sure you are aware of that.). here is another link:
http://www.hdtalking.com/softail_models/43776-mikuni_hsr_42_how_to_set_pilot_air_screw_idle_mixt ure.html

but that was last summer ! time flies !


after messing about with various o rings and settings and stripping and cleaning, and balancing, with no diffence apart from going from bad to worse, i just swapped the carbs for FCRs. problem still present.


that got us up to last feburary, so as far as running in circles, i guess i have already done that on the carbs ! i can tell you that i have read every publication i could find on Mikuni CV carbs and their operation for about 6 months.
now if you still suspect the pilot circuit, i'd be interested to know what you would suggest i do, that i havent done already !

I also dismissed the valves after getting them spot on a couple of months ago.

I have now dismiss the fuel pump and circuit, after swapping the pump, and getting similar behaviour. that was last week.

I am now in the process of checking the sensors. but rather than fork out for 2 new ones without even knowing if they are faulty (they measure OK), i though i'd confirm they are indeed duff first.

yesterday, i figured (to be cross checked) that only one cylinder (vertical) was at fault, and swapping the coils polarity just made it worse.
tonight, i'll put an oscilloscope on the sensors, and try to see if this happens:

http://www.picoauto.com/waveforms/vehicles/Ducati/wave110.html

If it does, i'll just have to order a new sensor. if it doesnt, i am stuffed.

i honestly dont see myself going in circles. i may be slow to work out the problem, but then again, i only give it a few hours a week, at most.

sorry, you got me worked up. :nash:

[Mr Gremlin]

i did wake up a bit grumpy LOL, trying to quit smoking isnt helping.
any way, the mix screw is only for the point of coming off tickover. ie when just cracking the throttle before actually getting the pilot jet working.
when confronted with a problem like this, everything has to be ruled out piece by piece before moving on to the next part.
a classic was a lass bought up an fzr400 up to me, she'd just bought it, 25 previous owners !!! massive folder of service invoices. did exactly what yours is doing. checked carbs, ok, stripped head off found several burned valves, re-built problem was better but still there at 6000 rpm on cruising. after hours on the dyno trying to find the fault, i eventually found it. makuni hadnt got the cross drilling on the pilot circuit correct, two opposing drillings didnt line up correctly so causing a restriction. this was on 2 of the carbs. i.m not saying this is your issue, but there is much more to the pilot system than the jet and mixture screw.
the air fuel mixing chamber o-ring is a very common fault, but very few people know of its existance, as is the bleed off holes blocking . have you checked these ?
if you take the float bowl off, remove floats etc, you will see an ali plug just behind the mixture screw housing, (its about 10mm round), this plug pulls out with pliers, do not twist it there is an o-ring around the plug that often perishes. with the plug out, you will see the mixing chamber which has 3 (normally) tiny holes which allow the fuel into the main venturi just behind the throttle butterfly, can you see daylight through all 3 ?

any failings in any of the above will cause your issues. so you can see what i'm getting at, rule out everything 100% before moving on to the next. your symptoms do not sound electrical thats why ive chimed in.

[utopia]

At the risk of repeating myself (repeatedly), I'm still not entirely sure that the fuel pump has been properly eliminated....though the replacement one may have been ok, I think it is by no means a certainty.
The single cylinder test seems to be homing in on something, but I also wonder (due possibly to my own electrical ineptitude) whether reversing the connections from one of the pick-ups has somehow caused a further problem.....?
If not, then the single cylinder test might finally verify the condition of the fuel pump, though still maybe not completely, due to the different angle of each carb perhaps.

Just a few minor observations to possibly add further confusion....sorry 'bout that.
Only trying to be helpful (and I do rather like a puzzle....beats f...ing sudoku anyway.....:rolleyes: )

[stef]

i did wake up a bit grumpy LOL, trying to quit smoking isnt helping.
any way, the mix screw is only for the point of coming off tickover. ie when just cracking the throttle before actually getting the pilot jet working.
when confronted with a problem like this, everything has to be ruled out piece by piece before moving on to the next part.
a classic was a lass bought up an fzr400 up to me, she'd just bought it, 25 previous owners !!! massive folder of service invoices. did exactly what yours is doing. checked carbs, ok, stripped head off found several burned valves, re-built problem was better but still there at 6000 rpm on cruising. after hours on the dyno trying to find the fault, i eventually found it. makuni hadnt got the cross drilling on the pilot circuit correct, two opposing drillings didnt line up correctly so causing a restriction. this was on 2 of the carbs. i.m not saying this is your issue, but there is much more to the pilot system than the jet and mixture screw.
the air fuel mixing chamber o-ring is a very common fault, but very few people know of its existance, as is the bleed off holes blocking . have you checked these ?
if you take the float bowl off, remove floats etc, you will see an ali plug just behind the mixture screw housing, (its about 10mm round), this plug pulls out with pliers, do not twist it there is an o-ring around the plug that often perishes. with the plug out, you will see the mixing chamber which has 3 (normally) tiny holes which allow the fuel into the main venturi just behind the throttle butterfly, can you see daylight through all 3 ?

any failings in any of the above will cause your issues. so you can see what i'm getting at, rule out everything 100% before moving on to the next. your symptoms do not sound electrical thats why ive chimed in.

umm, ok, i am not sure if i follow your description of where to look, but i think i have an idea of what you mean.
(http://www.hostingpics.net/viewer.php?id=115802jets.jpg where the green and blue arrow points ?)
if so, i have thoroughly cleaned the whole area, which wasnt that dirty. the bike, has less than 20k miles. It was running faultlessly for about 2 years, when it started playing up. so the misaligned holes or bad carb built can be ruled out. The bike is ridden mostly in the dry, from march to november, and ridden once in a while in the winter month. kept in a garage. it's not a justification to rule out the carbs, just another piece in the jigsaw.
also, the fact that i completely changed the carbs technology would certainly indicate that the original mikunis were fine..The FCRs certainly send the bike flying far better !

you say it doesnt sound electrical, but why would you say that ?
i would think that a duff sensor will have a signature, which could well be what i am seeing.
crusing dodgy because of a weak spark (if any), but full throttle OK because the voltage at the battery quickly hits 14V, rather than barely 12..
what would you say the symptoms of a wide air gap on a sensor would be ?

good luck kicking the habit.. has to be done !

[utopia]

Could I risk a brief hijack here and ask, Mr Gremlin, if you could confirm my suspicions about my honda dominator....?
It pops and bangs a little on the overrun, but this is somewhat controlable by holding the throttle ever so slightly open rather than shutting off completely.
Similarly, setting the tickover slightly higher has the same effect of reducing the problem.
I suspect a weak pilot setting (or blockage maybe), but thus far I haven't been able to shift the screw.
Just wondered if you, with your knowledge/experience of such matters, would confirm my suspicions...?

Sorry again for the total hijack.....I'm trying to keep it brief....a simple yes/no answer would suffice.

.......pauses to wonder whether to actually post this......oh sod it......if you don't ask......

[stef]

At the risk of repeating myself (repeatedly), I'm still not entirely sure that the fuel pump has been properly eliminated....though the replacement one may have been ok, I think it is by no means a certainty.
The single cylinder test seems to be homing in on something, but I also wonder (due possibly to my own electrical ineptitude) whether reversing the connections from one of the pick-ups has somehow caused a further problem.....?
If not, then the single cylinder test might finally verify the condition of the fuel pump, though still maybe not completely, due to the different angle of each carb perhaps.

Just a few minor observations to possibly add further confusion....sorry 'bout that.
Only trying to be helpful (and I do rather like a puzzle....beats f...ing sudoku anyway.....:rolleyes: )

no, you are right, its not a certainty, but like in medecine, you have to keep on adressing the issue with decreasing levels of probablity.
there was a large probability it was the fuel pump, before i swapped it. now, after swapping it, that probability has dropped.. next on the list is the sensor.
swapping the wires made it worse, because you then frankly upset the timing.
after the vertical finally gave up on firing, the remaining cylinder seemed to be pottling around fine, without any glitches or coughing.

this further reduces the probability of the dodgy fuel pump..

as i said, the oscilloscope on the sensor wire should be a good measure of its ability to produce an impulse.
those graphs are interesting. even more so if i can replicate the pattern.

http://www.picoauto.com/waveforms/vehicles/Ducati/wave110.html
the red is healthy.
the blue is dodgy, since it does produce a pulse, the coil is not broken (hence would read 100ohms). but the airgap is probably too wide to get the correct amplitude.

[stef]

Could I risk a brief hijack here and ask, Mr Gremlin, if you could confirm my suspicions about my honda dominator....?
It pops and bangs a little on the overrun, but this is somewhat controlable by holding the throttle ever so slightly open rather than shutting off completely.
Similarly, setting the tickover slightly higher has the same effect of reducing the problem.
I suspect a weak pilot setting (or blockage maybe), but thus far I haven't been able to shift the screw.
Just wondered if you, with your knowledge/experience of such matters, would confirm my suspicions...?

Sorry again for the total hijack.....I'm trying to keep it brief....a simple yes/no answer would suffice.

.......pauses to wonder whether to actually post this......oh sod it......if you don't ask......


:chuckle:
i'd definitely check the sensors.
..
emaybe carbon fibre mirrors would cure the problem ?

[Mr Gremlin]

Yup, the green arrow, the jet block needs to be removed first.
the o-ring perishes, so can leak fuel from the float bowl into the pilot system.
your thinking is correct with it one running ok, but changing the carbs to fcrs to eliminate the problem will add to confusion if the pilot system isnt set up for your engine configeration. fcrs are more tricky to set up than standard carbs.
did you change anything at the point where troubles started ? exhaust ? remove air box ?
if it was electrical, i doubt it would run faultlessly at tick over and full chat.
i had problems with a desmo due bike recently, that was electrical ( a duff battery ) and the electrics only seemed to fail once the voltage fell below 8v . there seems to be a lot of talk about air gaps etc on forums, but my experience has found it makes very little difference generally unless the gap is excessivly large. swopping the wires over can (on some pickups) determine the firing point in respect to the "tit" on the fly wheel, either rising edge or falling edge, but if you didnt change anything its not going to be that. :), so scope your pick up, you might as well rule that out as you've got the scope to do it, then thoroughly go through your makunis. and i mean thoroughly strip them, all jets out and inspected, hold them upto the light and check the holes look the same, soak them in acetone (nail varnish remover) to remove any gum.
fit them back on the bike and lets go from there. once youve got it running fine, then you can go back to the fcrs and get them dialled in :)

[utopia]

I think you have something with the carbon fibre mirrors idea......;)
Or maybe its tyre pressures....?

[stef]

Yup, the green arrow, the jet block needs to be removed first.
the o-ring perishes, so can leak fuel from the float bowl into the pilot system.
your thinking is correct with it one running ok, but changing the carbs to fcrs to eliminate the problem will add to confusion if the pilot system isnt set up for your engine configeration. fcrs are more tricky to set up than standard carbs.
did you change anything at the point where troubles started ? exhaust ? remove air box ?
if it was electrical, i doubt it would run faultlessly at tick over and full chat.
i had problems with a desmo due bike recently, that was electrical ( a duff battery ) and the electrics only seemed to fail once the voltage fell below 8v . there seems to be a lot of talk about air gaps etc on forums, but my experience has found it makes very little difference generally unless the gap is excessivly large. swopping the wires over can (on some pickups) determine the firing point in respect to the "tit" on the fly wheel, either rising edge or falling edge, but if you didnt change anything its not going to be that. :), so scope your pick up, you might as well rule that out as you've got the scope to do it, then thoroughly go through your makunis. and i mean thoroughly strip them, all jets out and inspected, hold them upto the light and check the holes look the same, soak them in acetone (nail varnish remover) to remove any gum.
fit them back on the bike and lets go from there. once youve got it running fine, then you can go back to the fcrs and get them dialled in :)

yep, i guess that would be the next step! (please god, if you ride a duke, make it that it's the sensors !)

re: the oring, yes, i confirm. i had it go dry on my previous monster. was this way when i got it. one cylinder would just get a black plug very quickly.
not the case on this one though. jets are snug.

Re: the FCRs. i read somewhere they were far easier to setup than the mikunis..
which is why i havent touched them since i bought them.
I fitted them on, and the engine was ticking over after half a second on the starter motor.. i was well impressed !
i was expecting to struggle like you do on mikunis that have been standing for 2 months.

[Mr Gremlin]

Could I risk a brief hijack here and ask, Mr Gremlin, if you could confirm my suspicions about my honda dominator....?
It pops and bangs a little on the overrun, but this is somewhat controlable by holding the throttle ever so slightly open rather than shutting off completely.
Similarly, setting the tickover slightly higher has the same effect of reducing the problem.
I suspect a weak pilot setting (or blockage maybe), but thus far I haven't been able to shift the screw.
Just wondered if you, with your knowledge/experience of such matters, would confirm my suspicions...?

Sorry again for the total hijack.....I'm trying to keep it brief....a simple yes/no answer would suffice.

.......pauses to wonder whether to actually post this......oh sod it......if you don't ask......

could be, or just an air leak maybe on intake rubbers , or just your exhausts are too short and loud and sucking fresh air back up igniting any unburned fuel . as i tried to explain earlier, the mix screws are really just for tick over and the tiny point when opening the trottle, easiest way to check for leaks is to spray a small amount of easystart over the rubbers (with engine running ) and seeing if there is any change of engine tone.

[Mr Gremlin]

yep, i guess that would be the next step! (please god, if you ride a duke, make it that it's the sensors !)

Re: the FCRs. i read somewhere they were far easier to setup than the mikunis..
which is why i havent touched them since i bought them.
I fitted them on, and the engine was ticking over after half a second on the starter motor.. i was well impressed !
i was expecting to struggle like you do on mikunis that have been standing for 2 months.

they can be if bought new for your specific bike, but often second hand ones have been fiddled with, also accelerator pumps etc add another dimension. standard carbs are a bit easier to sort out IMOA. but exhaust / air box mods / engine wear still require a specific fuel curve to be created.

yep, i guess that would be the next step! (please god, if you ride a duke, make it that it's the sensors !)

re: the oring, yes, i confirm. i had it go dry on my previous monster. was this way when i got it. one cylinder would just get a black plug very quickly.
not the case on this one though. jets are snug.

.
if the bleed holes are blocked it would be lean

[utopia]

Thanks for that.
Tbh, the rubber intake manifold also a little suspect......I fitted a replacement engine due to an oil-starved top end, and things didn't seem to align perfectly, though I tried to ensure that any leaks were on the airbox side of the carb, rather than the manifold side.
Exhaust is a predator, and certainly doesn't look too short. It is loud...ish though, despite being E-marked. And I have no idea whether the previous owner who fitted it made any adjustments to the fuelling, though I suspect not.
Anyway, thanks again, and sorry for hijack again.

Btw folks....the single cyl, air-cooled, torquey dommie makes the ideal cheap hack to partner your beloved monster and keep it free from winter salt and too many cold starts for short journeys.
I can get my fishing tackle on it too.
And two bags of building sand, as it happens.

[Ducmon]

swapping the wires from the pickups would make the problem worse because you will be changing the advance/retard of the timing. This is why I had to find out which way to wire the pickups when I replaced them.

[stef]

they can be if bought new for your specific bike, but often second hand ones have been fiddled with, also accelerator pumps etc add another dimension. standard carbs are a bit easier to sort out IMOA. but exhaust / air box mods / engine wear still require a specific fuel curve to be created.


if the bleed holes are blocked it would be lean

the FCR came from a similar bike/year/setup (apart from the exhaust brand, which i dont know !)
I just assume i will not be miles out in settings (and usually, close enough doesnt mess your ride the way mine is ! I may not be optimum, but still rideable)
and that fuel pump is sooo lovely ! you can hear it dropping a little shot glass of petrol in the engine when you open up !
but anyway, if the sensors check out, i'll be back to the carbs.

[stef]

Right, Now... who was it that suggested my sensors were faulty ?
http://i47.photobucket.com/albums/f168/stephane_david/bike/DSC_2081.jpg
http://i47.photobucket.com/albums/f168/stephane_david/bike/_DSC2079.jpg

I wired the scope on the sensor terminals on the CDI. qnd the two waveforms look pretty good to me.
24Vpk-pk, 10KHz at idle. both spikes with the same amplitude. and phase from 2 to 1 at around 158 degrees (that's 22degrees the other way round.)
here is a pic of the behaviour at higher revs.



http://i47.photobucket.com/albums/f168/stephane_david/bike/_DSC2084.jpg
I revved up a little and let the engine settle, got 40V pk-pk, but still no sign of a weaker pickup.

soooo...
now..


those carbon fibre mirrors...

[utopia]

Excuse my ignorance, but does that pick-up test also show whether the timing is ok too ?
....or maybe at least that, if the horizontal cylinder is assumed to be ok (since it runs ok), then the vertical is timed the appropriate amount out of phase, as it were ?
As well as confirming the ign timing, could this also eliminate or reduce the spectre of the loose flywheel nut ?

Tempted though I am, to attribute the farty noise to it having been "given the beans" a little too often, I think it would be ill advised.

I'm not even going to mention the fuel pump.
Or the tyre pressures.
Maybe the vertical cylinder has vertigo.

[stef]

oh Feck....
I think i worked it out this time.
and i am afraid to say i am the worse mechanic i ever had the displeasure to meet.
If stupidity gives you wings, i'll definitely be squad leader.. no general maximus at the air command.

that small knob on the FCR, hanging by that 15cm piece of cable...it's not the idle speed adjuster, is it.. is it a choke, by any chance ?
are you supposed to turn it down a little as the engine is getting warm ?

does anyone know ?

[Zimbo]

oh Feck....
I think i worked it out this time.
and i am afraid to say i am the worse mechanic i ever had the displeasure to meet.
If stupidity gives you wings, i'll definitely be squad leader.. no general maximus at the air command.

that small knob on the FCR, hanging by that 15cm piece of cable...it's not the idle speed adjuster, is it.. is it a choke, by any chance ?
are you supposed to turn it down a little as the engine is getting warm ?

does anyone know ?


It's the idle speed adjuster, you turn it up to start the bike as it hasn't a choke and won't idle when cold on standard setting, and turn it down once the bike is warm to reduce the idle revs to an appropriate level.

[stef]

It's the idle speed adjuster, you turn it up to start the bike as it hasn't a choke and won't idle when cold on standard setting, and turn it down once the bike is warm to reduce the idle revs to an appropriate level.

so, what happens if i dont wind it down.. is it likely to cause the symptoms i am observing ?

[Zimbo]

so, what happens if i dont wind it down.. is it likely to cause the symptoms i am observing ?

The bike will run as normal, but the idle speed will be increased to possibly 2000 - 3000 rpm.

Actual running otherwise shouldn't be affected, it's just an idle speed adjuster.

[gary tompkins]

Would just make bike tick over too fast when warm

Have you checked all the HT side out - plucgs, caps, coils and leads?

[stef]

The bike will run as normal, but the idle speed will be increased to possibly 2000 - 3000 rpm.

Actual running otherwise shouldn't be affected, it's just an idle speed adjuster.

ah, dammit.
ok, back to tuning the carbs then. i found a couple of good sources on tuning FCRs. could be useful to read them.
thanks !

[utopia]

But, as you have already said, the symptoms were similar with both sets of carbs, so its likely that the problem lies elsewhere.....while remembering of course that all such assumptions are dangerous if taken as gospel truths.

[stef]

But, as you have already said, the symptoms were similar with both sets of carbs, so its likely that the problem lies elsewhere.....while remembering of course that all such assumptions are dangerous if taken as gospel truths.

yep, but i have to admit defeat here, and take my words back.
first set of carbs may have had a leak somewhere (i couldnt source a repair kit, apart from some of the orings, which cost me an arm. which is why i decided to get FCRs)

and i havent done anything to check the FCRs ..they might need tuning.
at least i very likely have eliminated all other possibility?
can you see something else ?

[utopia]

can you see something else ?

Nope....sorry.
But I will continue to ponder.

[Mr Gremlin]

have you done a hot and cold compression test ?

[Capo]

Those scope pics are on the money.

[utopia]

Those scope pics are on the money.

I thought that too.
And the fact that all the keys are in french adds a certain character, somehow.

[stef]

have you done a hot and cold compression test ?

no, mainly because the bike pulls much better than it has ever done.
and also because i dont know how to.

[stef]

I started on the FCR tuning tonight.
I am taking the hypothesis that the bike is rich (very) at 0 to 1/4 throttle.
first of all, i checked the fuel screw and slow screw for the starting settings:

fuel screws were 1 turn out each. -> no scope for leaness on those then !
that means the slow air screw is wrong.

slow air screw were 1.5 turns out. i set them to 2 turns out, leaving the fuel screws at 1 turn out.
refering to the tuning guide, thats going from a 125 to a 135 slow jet.
i went for a test run, and the same symptoms were present: coughing at 0-1:4 throttle.
back at the shop, i checked the plugs, they were both black.
I guess i am still too rich, and will try for a 3 turns out on the slow air screw next time.

[Capo]

Take your screwdriver with you.

[stef]

Take your screwdriver with you.

dont fancy stopping on the side of the country road without knowing for sure i will be able to get the bike going again !
its a long and lonely walk...

[Mr Gremlin]

can you borrow a compression tester ?

[stef]

can you borrow a compression tester ?

not without really looking for one, but if you reckon it's definitely worth a shot ?
how could i lack compression, if the bike is pulling hard ? and why would that blacken the plugs ? (genuine question of a budding mechanic with limited knowledge)

I could see how it would make the bike struggle at low rev, but what i see is more like a misfiring than a difficulty to pull its weight, if you see what i mean.

[gary tompkins]

If the electrics check out and you are getting a good spark

My money would be on FCR's needing re-jetting going by the sooty plugs

[Capo]

not without really looking for one, but if you reckon it's definitely worth a shot ?
how could i lack compression, if the bike is pulling hard ? and why would that blacken the plugs ? (genuine question of a budding mechanic with limited knowledge)

I could see how it would make the bike struggle at low rev, but what i see is more like a misfiring than a difficulty to pull its weight, if you see what i mean.

Given your problem and your results so far, I would want to know that everything in the combustion cycle was OK, you need compression, fuel and a spark.

[Mr Gremlin]

not without really looking for one, but if you reckon it's definitely worth a shot ?
how could i lack compression, if the bike is pulling hard ? and why would that blacken the plugs ? (genuine question of a budding mechanic with limited knowledge)

I could see how it would make the bike struggle at low rev, but what i see is more like a misfiring than a difficulty to pull its weight, if you see what i mean.

the engine should be checked to make sure all is in order before playing around with anything else.
if you had a leaking valve (for example ) the wider you open the throttle and the more the engine revs, the lesser effect a little bit of leakage will have, but as your problem is at cruising throttle , pulse waves, scavenging etc can all be affected by a low compression.
so check out the basics first.
compression,
valve timing
ignition timing (i think you've already done this ??)
if all is in order, then s0d about with the carbs. if you dont , you will be wasting your time :(

[stef]

ok, i am on the lookout for a compression gauge.

[stef]

Ok, before i spent money for nothing on a compresion gauge, i thought i'd try tuning the FCR to the max: so that's 3 turns out for the slow air screws, which is supposed to make the mixture as lean as possible. I also swapped the plugs from DCRP8E to DPR8EA-9.
i went for a quick ride, 20Km or so.
the bike seemed better. not perfect, but almost enjoyable. It may just be because of the out side temperature, the day of the month, who knows.

so to me the problem isnt solved, and could still be a carburator tuning issue, eventhough i have been through all the slow air settings without finding a lean one.
however, leaning the mixture helps. plugs are still rather black, but a little less so.
I also did the throttle blip test, as suggested on the FCR tuning guide, and indeed, the bike runs rich.
The next step would be to change the main fuel jet, should i go for it ?

later: i have now checked the main jet, its a 150. is that wide ? small ? only replacement i have at hand is a 155.


as an aside, if by any chance, i had some leak around the piston ( to be shown by a compression test), would that explain the fogging behind the oil sight glass ?
this bike as always had this, even when runing fine. i left the oil cap opened many times overnight to try and get rid of it, but it always comes back.

[gary tompkins]

Fogging is caused by condesation of water trapped in the oil. Suggests the engine isn't getting up to temperature.. either running in cold weather or not run long/hard enough. I found removing the breather catch tank and running a K&N on crankcase helps reduce this. An engine running rich will also run cooler than one set up properly.

[stef]

Fogging is caused by condesation of water trapped in the oil. Suggests the engine isn't getting up to temperature.. either running in cold weather or not run long/hard enough. I found removing the breather catch tank and running a K&N on crankcase helps reduce this. An engine running rich will also run cooler than one set up properly.

thanks, useful info (although i already have the k&n on the cranckase) still, it could be because it's running rich.

[utopia]

..(condensation in the oil)....... it could be because it's running rich..

The chances of the two being linked are very slim, in my opinion.
As you probably already know, all engines are subject to pressure cycling below the piston as well as above it, the former being vented through the crankcase breather.
This means that ambient air is drawn into the cases as the piston rises (and pumped out again as it falls).
On most days this air will be humid to some extent, and the moisture it contains will condense inside the crankcases and combine with the oil to cause emulsion and the fogging that you describe.
Its worse on a v-twin due to the size of the pistons and the phasing of their stroke (ie in a four cyl the upward movement of one piston is partially cancelled by the downward movement of another, whereas in the v-twin they act somewhat in unison).
Its even worse on a big single.
My 650 (single) Dominator suffers badly from this....the uppermost region of the crankcases is the little chamber that houses the drive gears from the starter motor, which is mounted on top of the cases behind the cylinder. I have recently discovered that this is where a lot of condensation can collect, as the chamber is not vented. I removed about a tablespoonful of nasty condensation sludge from there, as well as about a teaspoonful of pure water....!!!! This hadn't done the bearing a great deal of good. Fortunately, I have a spare engine to cannibalise for bits, though this one had condensation present too, but nowhere near as much, and the bearing was still ok.
Like Gary says, short journeys where the engine doesn't get fully hot will worsen the situation.....The Dommie does get used for many short journeys, often in cold, damp conditions, as it is my winter hack.
I guess piston blowby could add to the problem, but I wouldn't use the presence of condensation as any sort of indication of a particular fault in the engine. They all do it to some extent.
Even my Z1 used to get fog in the sight glass.

[stef]

right, i think it's getting there.
I adjusted the float height the other day, and went for a 30km ride yesterday. it still does have the odd coughing, but only when the engine is not loaded at all, at say 1/8 throttle, on a gentle down slope.
and it's much less than it used to be.
in any other condition, the bike feels great, picks up fast, and does not hesistate.
after the ride, i checked the plugs: horizontal was good, medium to dark chocolate brown.
the vertical was a bit darker.
to sum up everything i did on the carbs:
-idle screw out 1 turn (leanest)
-slow air out 3 turns (leanest)
-needle clip on position 2 (1 from leanest)
-floats at 9.6mm (from 9mm)

with this, i can have a ride, and almost forget the bike has a slight problem.

[gary tompkins]

The fact that you've had to lean everything out to get it to run suggest jets are too big

[stef]

yes, i'd think so, but i cant find a reliable value for what the jet should be on my setup.
I am currently at 150.

[Kato]

These are the base setting I've always used they were given to me by Chris at CA Cycleworks, he also presets all the FCR's he sells with these setting and guarantees them to be within 10% straight out of the box on a 900.

Fuel screw mixture screw 3/4 turn
Slow Air Screw 1-1/2 turns
Float height 9mm
Main Jet 155
Main Air Jet 200
Slow Jet 60
Needle EMT
Needle Clip 3rd from top

[stef]

These are the base setting I've always used they were given to me by Chris at CA Cycleworks, he also presets all the FCR's he sells with these setting and guarantees them to be within 10% straight out of the box on a 900.

Fuel screw mixture screw 3/4 turn
Slow Air Screw 1-1/2 turns
Float height 9mm
Main Jet 155
Main Air Jet 200
Slow Jet 60
Needle EMT
Needle Clip 3rd from top

cheers !
the needle is good, the jet is 150, but i have a set of 155. the rest is not far off.
but if those are for a 39mm FCR, then going to 145 jet would be a bit far off the base settings, no ?

[stef]

right, after about 150miles with the latest settings, it looks like the problem is solved.
i ended up with:
-3/4 turns on the mixture screw
-150 main jet
-clip on 2nd groove
-slow air 3 turns out (max)
-float height 9.6mm
-EMT needle

the bug mainly came from a float height, the rest is probably just marginal.
there is probably room for further tuning, but since it's riding season this will wait.

Thanks again for all those who helped during these difficult times !