running rich - still?!

[don_matese]

Any ideas of whats causing this issue

Background
A while ago my bike was running very rich, since then, I've replaced the ignition coils, spark plugs, fuel and air filters and then had the mixture sorted. Its also been idling a bit slow so i raised the idle at the weekend.

Current Issue
Outside temp: 4-8Centigrade
I start the bike up on the choke (1996 Carbed M600) and let it warm up for a minute or two, then drive to work (2-3 miles). when I come to traffic lights unless I keep the throttle open manually the engine dies - both on and off the choke.

However, If I twist the throttle WIDE open then a whole bunch of soot comes out of the exhause and the bike runs fine without stalling. I'd rather not give it the beans outside my house every morning...

Current thinking
I am thinking either the mixture is still too rich
or the idle is still too low and causes me to have to richen the mixture too long with the choke which is fouling the plugs...

Any other ideas of what to check or may be causing the problem?

[Sirc]

sounds like your diagnosis is spot on - you definitely need to stay off the choke if possible, is there any chance that you can ride it sooner rather than let it idle for a kick-off? It could be that your idle mixtures screws need adjusting - they could be wound too far out. Do you know if you have a Dyno jet system fitted as if so then you need to have a free(er) flowing air filter fitted. Do you ever give the bike a blast or is it constantly at low revs around traffic? It could be your plug grade needs looking at - a look at the plug colour at various conditions would help here.

[stef]

it's not carb icing, is it ?
my used to suffer from this on cold morning. it's crippled the carbed monsters since day 1

have you tried just stopping the engine (when it starts playing up, at the light)
let it rest for a couple of minutes and start again.
if it's carb icing, the bike will be good for another couple of miles.

very unconvenient, but at least you eliminate this as a potential cause.

[don_matese]

Dont think its icing - when it dies I have to give it plenty throttle for it to catch again...

[gary tompkins]

Are you sure the choke mechanism or cabe is working properly?

The choke could be sticking on

[Gerry]

If it's carbed model ..... a sticky float ?or needle not seating correctly.

[stef]

If it's carbed model ..... a sticky float ?or needle not seating correctly.

also a dry seal around the main jet. had one of those once, the vertical cylinder kept fouling its plug.

[Sirc]

answering my own question Don - (as you didn't!) - if your typical week in/week out journeying is 2 to 3 miles there and back with rarely a blast on a long journey then this is almost certainly a factor here.

[don_matese]

yes it is - more recently because of ill health, but had been limited due to the richness of the mix - didnt want anything happening to the cylinders or pistons.

I'll try giving it the beans tonight on the way home and go a 10-15 mile route home instead :)

[utopia]

You say that you've had the mixture sorted though, so I'm still wondering about carb icing.
The symptoms you describe do sound that way.
It doesn't have to be that cold for it to happen, its mostly dampness/humidity that causes it.
Might be worth trying some pro.fst in the petrol to eliminate the possibility before getting the spanners out....you'll need some sooner or later on a carbed motor anyway.
I would suggest a double dose...mine still ices on a single dose.

[Sirc]

Don't worry about going for a blast with a rich set-up Don - it's far better that way than if it were running lean. Hope it helps.

[don_matese]

Yeah I know running rich will help keep the cyls cooler but it was so rich I was only getting 64 miles to my tank of fuel... I must have been leaving a trail of petrol behind me all the way home!

[Sirc]

I see what you mean - in a way, you've already confirmed that there is something seriously wrong, something that won't be cured just by blowing the cobwebs away. Might be worth remembering back to a time when it was running ok (if such a time exists even) and trying to remember the sequence of events/repairs/replacement parts that lead up to now. Could be a full carb strip/clean/tune could be the answer, but then again..

[utopia]

I can hardly imagine getting such poor mileage from a tankful.
I'm surprised it ran at all.
I get 150 before the light comes on.
Could the tank have been leaking ?

I've also heard claims that over-rich mixtures wash oil from the bores, leading to piston slap.....though I'm merely repeating the views of others...dunno the ins and outs myself.
Still better than lean though, I would say.

[don_matese]

I think a little history might help

1. yes the original tank was leaking so I got a new one
2. Original carbs had been varnished right up so got all new needles, jets, seals etc and fully rebuilt them
3. Spark plug cap for one of the cylinders had packed in so got a new one
4. on the safe side I got a "new" set of coils and tested them out to make sure they were better than my old ones
5. checked compression ~130psi on each cyl
6. new sparkplugs based on the comments in here: NGK iridiums but i reckon I'll go back to the updated stock champions

after all that it was running really rich - i didnt have the tools or the time to sort the fuelling out properly so i took it to a garage - its doing much better now but still has an issue on the horizontal cylinder.

I have noticed that theres a bit of fuel sweating all over the carb servicing the horizontal cyl - i think as has been mentioned by sirc that its the float height thats incorrectly set.... ah well a weekend job for me :)

[gary tompkins]

Are you sure ignition is 100% on both cylinders. A faulty H/T coil, ignitor or CDI pick-up could cause a weak spark, which will foul plug an give symptoms similar to over rich running.

[don_matese]

Yep, I swapped the ignition coil and the issue switched to the other cylinder so replaced it with a working ones.

I have found recently that I have to switch the fuel off at night or i find that when I take the cover off it smells heavily of petrol.

[Nickj]

If it's leaking fuel standing then you might want to go back and check the float(s), float height(s) and that they do shut the flow of fuel off when at their correct setting (is the valve seat OK?).
Also when you put the new jets in how did you clean the carb bodies?? There would have been a layer of old yuck emulsion through the inside which can drop off and give odd problems. Ultrasonic cleaning will get all of the crud out of the carbs, if you can't find anyone to do that then stripping the bodies and tossing them into a pan of water and boiling them works. It will trash any rubber seals though but viton will be OK.
Blow through all the airways with compressed air or a can of carb cleaner to get any moisture out. Reassemble and start from scratch.
If you want them really clean add a little lemon juice, the only problem there is that you can end up with a matt finish

[Sirc]

how's the bike going Don - any improvements?

[don_matese]

yep :) all sorted now. Carbs apart and cleaned, then tweaked by a local friendly mechanic, and finally found that my rear wheel had been missing the spacer so it had been tightened right up by the tyre changers to keep it in place... needless to say I will not be going back there!

[Sirc]

Good to hear news Re: carbs/running