Compression test cold engine...

[Dukedesmo]

I realise that a compression test should be done with a hot engine but as I have removed the exhaust and other parts required to run the engine that's not really practical at the moment.

As some of you will know I rebuilt my engine last year and have been running it through this year, have done around 2,500 miles and it runs very well, makes good power but is using too much oil, I was hoping it was just a running-in problem but it's not improved with the mileage. :(

Not certain if the oil usage is valve guide seals or rings, I plan to swap the valve guide seals for some better ones (the OEM seal looks like the tip off a condom) but will probably end up taking the heads/cylinders off to check for any ring-related issues, although I would prefer to not have to do this if I can be certain it is valve seals.

Anyway before all this I wanted to check the compression to see if there is any problem, should have done it before dismantling anything but as I wanted the swingarm off I needed to remove the exhaust etc. and would prefer not to have to reassemble everything to do a 30 second test.

So, what I'm asking is what difference would I expect to see by doing a compression test on a cold engine as opposed to a hot one?

For the record a cold test shows 170psi in both cylinders.

[Saint aka ML]

I done a test on cold engine last year on my m944.

190PSI front and 188-189PSI rear.

My one always was using some oil, my stock m750 was using oil. Frankly in manual it says it can loose oil and I think it is about 400-500 ml for each 3-4k miles.

My one was using on the 500ml side if used hard, if town work about 250ml.

How much is your using?

[Dukedesmo]

How much is your using?

Around 1L per 1000 miles. :eyepopping:

I'd be happy with 500ml per 3-4k...

[Saint aka ML]

Around 1L per 1000 miles. :eyepopping:

I'd be happy with 500ml per 3-4k...

Ok I would also strip it again ;)

Stupid question did you check air-box. My last huge increase in consumption was because it was spitting it to airbox.
With that compression I do not think I have engine issue but rather blocked crank return valve all pending further look on my side in december.

[slob]

^^^
what he said, I've had quite a bit of oil in my airbox and will probably make a larger breather/seperator box in the long run.

[Saint aka ML]

^^^
what he said, I've had quite a bit of oil in my airbox and will probably make a larger breather/seperator box in the long run.

I will go step further and use advice already posted here.

I keep same setup as I have however I drill out the crank one way valve so it is used only to attach the tube (hollow inside). Tube goes to expansion tank, if you can make bigger expansion tank great. Then feed to airbox however just before airbox I will fit a one way valve in to the rubber line.

It is I believe how it is on race bikes. It effectively increases size of expansion tank, allows oil to drain back quicker and if your one way valve gets cloged or damaged easy swap.

[Dukedesmo]

Not got an airbox - split FCR's on individual filters.

But I have an open (no reeds) breather into the catch tank and then a long hose to a Corse reed-valve breather which is situated in the carb area but hasn't leaked any oil, so no blow-by.

There are signs of some oil passing through the exhaust valve stem seals (burnt on), hard to see any on the intakes, the plugs are not too oily (although front cylinder plug is slightly blacker than the rear) so I'm wondering if it's the valve seals leaking, with the oil passing the intake seal getting burnt in the cylinder but the oil passing the exhaust seal going straight out the exhaust?

[Saint aka ML]

Not got an airbox - split FCR's on individual filters.

But I have an open (no reeds) breather into the catch tank and then a long hose to a Corse reed-valve breather which is situated in the carb area but hasn't leaked any oil, so no blow-by.

There are signs of some oil passing through the exhaust valve stem seals (burnt on), hard to see any on the intakes, the plugs are not too oily (although front cylinder plug is slightly blacker than the rear) so I'm wondering if it's the valve seals leaking, with the oil passing the intake seal getting burnt in the cylinder but the oil passing the exhaust seal going straight out the exhaust?

Could be but that would be rather visible behind you.

How do you know you lost 1l in 1000 miles?

Did you allow for fact that when running in it will burn more, you 100% certain you filled it up to correct amount? If you have bigger oil cooler how much bigger?

I had a situation where I could not fill up the engine with correct amount of oil due to air block. After turning the engin over for about 30s I manged to put in another 750ml.

[Dukedesmo]

I can't say I've noticed a 'fog' behind but there is some smoke when revving, maybe it smells oily from behind?

A few years back I had a similar oil drinking problem with the 916 and it was never really noticeable, except for an oily smell - new valve seals & piston rings cured that but the Monster has new seals/pistons/rings/bores?

I was certainly expecting to use some during running-in but would think that it should have settled down by now?

At the moment it is running with 2 standard oil coolers to keep the temperature down (1 above, 1 below the front cylinder) but I am going to swap them for 1 larger cooler. I am circulating more oil, faster and specifically to the heads so any seal leakage may be more noticeable?

I've been topping-up and monitoring oil levels after every ride, it is consistently requiring a top-up of around 1L/1000 miles so I'm certain that something's not right.

At this point I'm just looking at the possibilities but although the bike runs well, I'll be doing a bit of refresh/revision over the winter - basically addressing a few issues that I'm not quite happy with and making some upgrades. Next year's model will be even better; same concept/looks but with some improved details... :thumbsup:

[Dukedesmo]

will probably make a larger breather/seperator box in the long run.

Would be interested to see what you come up with. :thumbsup:

I've been considering this as the stock box is very small but where to fit a larger one would be a problem...

[utopia]

I didn't notice any oil smoke from the exhausts when I was following you to East Kirkby earlier in the year. ...not that I was particularly looking for it, but it wasn't obvious anyway.

Glad to hear you're doing some further finishing upgrades ....stick it in for bike of the year again next year and hopefully it'll win this time ...like it should have done this year, in my opinion.

[Saint aka ML]

Would be interested to see what you come up with. :thumbsup:

I've been considering this as the stock box is very small but where to fit a larger one would be a problem...

Which frame did you use as IE frame has a bigger box alredy then stock carbed. Then looking at both of them you could make it even bigger as carb box is quite bigger in one place where as in IE model you left with empty space.

[Dukedesmo]

I didn't notice any oil smoke from the exhausts when I was following you to East Kirkby earlier in the year.

Yes, I've not noticed it other than the level dropping - must be well 'diluted' by the time it gets out. :D

[Dukedesmo]

Which frame did you use as IE frame has a bigger box alredy then stock carbed. Then looking at both of them you could make it even bigger as carb box is quite bigger in one place where as in IE model you left with empty space.

Carby frame, box is small and not really anywhere to fit another or bigger box, unless pillion seat hump can be replaced?... :scratch:

[Saint aka ML]

Carby frame, box is small and not really anywhere to fit another or bigger box, unless pillion seat hump can be replaced?... :scratch:

Yes it can. There was a guy in Holland that has cut pillion seat part off. Fitted hinges to the pillion cover and made a storage box.

Option 2 is removed under-tray. Then make a box that fits instead of it with bigger hump where tool-box would be.

[Rockhopper]

I'd be interested to see your compression test results. If you've taken 2500 miles to run it in I wonder if you have been too gentle with it and glazed the bores?

[Dukedesmo]

I'd be interested to see your compression test results. If you've taken 2500 miles to run it in I wonder if you have been too gentle with it and glazed the bores?

Results were 170psi both cylinders, I'm thinking it should have been more given the HC pistons?

Could be that the initial run-in was not hard enough as it was running lean and I didn't want to give it a handful due to pinking.

By the time it'd been on the dyno and fuelling sorted it may have already glazed?

I will be removing the heads & cylinders to check/remedy this and the next run-in will be more 'determined' with plenty of cylinder pressure... ;)

[Mr Gazza]

This is probably out of date and possibly not relevant to a more modern engine like a Ducati, but...

In the "olden days", well the sort of eighties era anyway, there were a range of superior lubricants available, I am thinking of Silkolene specifically.
These were claimed and believed to be far better than previous oils, and came in "Straight" grades more suitable for the British Irons I used to ride.

It was said that the fancy oils were too good for running in a newly built engine, and that it would not bed in properly.
So what lot of us used to do, was to run in with a cheaper, high detergent oil of the correct grade. Making sure that lots of oil changes were given during the run in (First one was typically at 100 miles as I recall).
Then on to the good stuff once happy that the motor was run in.

This was all probably more ritualistic than scientific, and I am not sure if it would have any significance applied to a modern motor and modern oils (Still a large air cooled twin though.?)
Perhaps it would seem wrong now, to put some cheap multigrade into a nice newly built Ducati.?.... Thoughts anyone..?

Duke, I think you said that your bike was getting rather hot when first got it going, and I also think I remember a picture of your bike with very discoloured exhausts early on in the run in? Maybe it just got too hot and cooked the oil onto the bores??

[Dukedesmo]

Duke, I think you said that your bike was getting rather hot when first got it going, and I also think I remember a picture of your bike with very discoloured exhausts early on in the run in? Maybe it just got too hot and cooked the oil onto the bores??

Yes, the fuelling was out due to new carbs being way too lean and the ignition was also behaving erratically so it did run very hot & lean initially. I soon got it setup on the dyno but the damage may have already been done by then?
Temp sensor fitted to the front cylinder head, here's a pic taken whilst running in the early days - note the temp 134 degrees. :eek:

http://www.ukmonster.co.uk/monster/attachment.php?attachmentid=17459&stc=1&d=1386439882

It's running more sensible temperatures now so, hopefully nothing that can't be sorted. :thumbsup:

[Saint aka ML]

I must say 134 is not the highest I seen a monster run at.

[Dukedesmo]

Dismayed by the low compression readings from the last test I repeated the test but with a squirt of oil in the cylinders first to ensure a good ring seal, results were;

Vertical cylinder 228psi, Horizontal 215psi.

These figures are more like the 'high compression' that the pistons are designed for. I think the front cylinder reads lower because I may not have got oil all round the bore due to it being horizontal but going by the rear cylinder reading it seems I am well down on what I should have.

I was going to take the cylinders off anyway but this confirms that something is not quite right.

[Saint aka ML]

But good or bad rings you will always have higher compression with bit of oil no?

I mean there is no perfect seal between rings and bore as friction would be to much hence oil ring ...

[Dukedesmo]

Probably but a 25% drop? Either way there's definitely something not right and I've got to do something over the winter. ;)

[Capo]

But good or bad rings you will always have higher compression with bit of oil no?

I mean there is no perfect seal between rings and bore as friction would be to much hence oil ring ...

The purpose of the oil ring is to prevent oil on the bore entering the compression chamber and the compression rings, some are designed to srcape the oil from the bore on the down stroke.

DD has followed correct procedure and noted an increase in pressure when oil was introduced into the combustion chamber which points to a ring sealing problem, had there been no significant increase in pressure then the sealing of the valves would be a suspect.

[Saint aka ML]

Probably but a 25% drop? Either way there's definitely something not right and I've got to do something over the winter. ;)

Hehe

The purpose of the oil ring is to prevent oil on the bore entering the compression chamber and the compression rings, some are designed to srcape the oil from the bore on the down stroke.

DD has followed correct procedure and noted an increase in pressure when oil was introduced into the combustion chamber which points to a ring sealing problem, had there been no significant increase in pressure then the sealing of the valves would be a suspect.

Thank you that is informative Capo.


Quick question, when you do compression test do you remove both sparkplugs as well?

Last one I did I got about 200psi but I had one plug in at time of test.

[Kato]

Lukaz: I always remove both Plugs to do a compression test but it's just my preference,


Duke D: From all that I've read here I'd have to agree with Stuart and say rings, it might be as simple as some burnt oil has gummed them up and a good clean will sort it out, if that's the case then a quick hone of the barrels and give the rings another chance to bed in, however if that does not work you'll end up stripping it down again to fit new rings, given that ring sets are relatively inexpensive I'd go with that option first.

[Dukedesmo]

Lukaz: I always remove both Plugs to do a compression test but it's just my preference,


Duke D: From all that I've read here I'd have to agree with Stuart and say rings, it might be as simple as some burnt oil has gummed them up and a good clean will sort it out, if that's the case then a quick hone of the barrels and give the rings another chance to bed in, however if that does not work you'll end up stripping it down again to fit new rings, given that ring sets are relatively inexpensive I'd go with that option first.


I did this test with the other plug out, seems better as it will spin over a little easier.

I'll see what it looks like in there, it was all new when assembled; new bores, new pistons & rings so hopefully easy to sort but, yes I'd rather buy new rings than do it all again.

I'll report back when I've started the surgery... ;)

[Kato]

There is another way but I'm not going to recommend it but can say from first hand experience that it works, I first saw this years ago when I worked for a fairly successful Touring car team, we had an engine with a similar issue apparently fairly common as motors were not generally run in properly, I was asked to go and fetch some Vim!!!!!! me thinking i was being lined up to clean something off I went, the guys had removed the air box and filters and with the motor held at fairly high RPM a handful of the aforementioned scouring powder was thrown into the air intake, the trick at this point is not to let go of the throttle, motor would bog down cough, splutter and spit but eventually come back to normal running ........Oil consumption reduced bores honed without dismantling and rings now seated........ Back out on the track, not sure you could even buy the stuff any more and off course these motors were rebuilt every couple of rounds but it did the job on more than a few occasions:shocked::shocked::shocked:

[Dukedesmo]

Think I'll leave the Vim in the kitchen... :eyepopping: