Oil Burn Issue

[Antiquar]

Okay, I'm back already. Having just "sorted" my G5 I've been riding it much more. I've noticed a smoking/oil consumption problem from the left cylinder.

It manifests as white smoke at idle and in stop and go riding (not a huge amount and easy to miss in daylight unless you're looking for it)--I don't notice any at speed. If I go for a jaunt on the freeway the smoke will seemingly stop.

Yesterday I ran compression and leakdown tests, and by those the top end is in good health. Both cylinders came in at 180-185psi and 2-3% leakdown at 100psi. Not surprising as I rebuilt the top end last year, including new cylinders, pistons, rings, and rebuilt heads with new valves/guides.

Oil in the sump is still clean after my last change (couple hundred miles ago). Pulling the left cylinder plug immediately after a ride reveals oil on the electrode and top plug threads. Right plug is perfect. Regardless of the burn issue, the bike runs very well with great power.

To me this sounds like a valve guide issue rather than rings. But I wanted to sound it out on the board before I dig into the left cylinder again. Any ideas? Anything else I should be looking into?

[Don G]

How many miles since the fix? perhaps it needs to be put under load to seat the rings?  DonG

[Antiquar]

Only about 500 miles with the new top end.

[Don G]

Well for now take her out and giver her the beans! It will clear up or not.  DonG

[John A]

yeah, Id sure get it warmed up and make it work like a borrowed mule for a couple hundred miles. especially with a good leakdown.

[guzzisteve]

 :1: then check again at 1Kmi

[Jurgen]

Okay, I'm back already. Having just "sorted" my G5 I've been riding it much more. I've noticed a smoking/oil consumption problem from the left cylinder.

It manifests as white smoke at idle and in stop and go riding (not a huge amount and easy to miss in daylight unless you're looking for it)--I don't notice any at speed. If I go for a jaunt on the freeway the smoke will seemingly stop.

Yesterday I ran compression and leakdown tests, and by those the top end is in good health. Both cylinders came in at 180-185psi and 2-3% leakdown at 100psi. Not surprising as I rebuilt the top end last year, including new cylinders, pistons, rings, and rebuilt heads with new valves/guides.

Oil in the sump is still clean after my last change (couple hundred miles ago). Pulling the left cylinder plug immediately after a ride reveals oil on the electrode and top plug threads. Right plug is perfect. Regardless of the burn issue, the bike runs very well with great power.

To me this sounds like a valve guide issue rather than rings. But I wanted to sound it out on the board before I dig into the left cylinder again. Any ideas? Anything else I should be looking into?

If the white smoke shows up, especially when decelerating, it definitely is an intake guide problem and probably won't cure itself.  Might be a guide seal coming loose if the bike has them. 
 J�rgen

[rodekyll]

Not completely cast in stone, but

Black smoke = fuel
blue smoke = oil
pink smoke = ATF
white smoke = water

I think you might be collecting water in the low side muffler and it's leaving as steam. 

[John A]

couple other things to check- breather trouble, fuel level in float chamber

[rodekyll]

Something else I thought of:

If you hold something cold behind the muffler -- like a refrigerated piece of metal -- whatever is spewing out the back will condense on the surface for easier identification.  A more flintstone-level test is to get your hand back there, let it get a good dose of the "smoke" and sniff it.  If it smells wet, it's water.  If it smells like that old Ford truck you hate to be behind, it's fuel or oil.

[Antiquar]

Not completely cast in stone, but

Black smoke = fuel
blue smoke = oil
pink smoke = ATF
white smoke = water

I think you might be collecting water in the low side muffler and it's leaving as steam.

I was really hoping that this was the case but oil on the plug wouldn't support water in the muffler theory. That said I'm still going to check for moisture, your cold metal trick sounds like a good idea.

[Antiquar]

couple other things to check- breather trouble, fuel level in float chamber

What's a good way to check for breather trouble? I can feel pulses from the atmosphere vent and get a drop of oil out of there occasionally. I have an old style breather box setup, the one with the two inlets to rocker cover vents.

And thanks for all the ideas everyone! Sounds like I should ride the damn thing some more before taking pulling it apart. That, and do some other less invasive tests.

[rodekyll]

I was really hoping that this was the case but oil on the plug wouldn't support water in the muffler theory. That said I'm still going to check for moisture, your cold metal trick sounds like a good idea.

How did you do the plug chop, and can you post a picture?  Close-up and good focus gets you extra points.

[lucian]

Oil rings take the longest to fully seat, give it more time, miles before  worrying too much. With 180 lbs readings I'd say your compression rings have seated fine. Also I would be running dino oil for the first 500 miles if you are not already.Check your air box, if you are still running it, to see if oil is being imported through the intake. 

[John A]

What's a good way to check for breather trouble? I can feel pulses from the atmosphere vent and get a drop of oil out of there occasionally. I have an old style breather box setup, the one with the two inlets to rocker cover vents.

And thanks for all the ideas everyone! Sounds like I should ride the damn thing some more before taking pulling it apart. That, and do some other less invasive tests.

That's about it, unless you take it out and visually look at it which I don't think is necessary

[lucian]

Do you have a sump spacer on that g5?

[Rough Edge racing]

 I believe if you pull the carb and intake stub you can see the intake valve? Take a look with a bright light, compare both sides, is the back of one valve, or both, oil covered ?

[Antiquar]

How did you do the plug chop, and can you post a picture?  Close-up and good focus gets you extra points.

No proper plug chop. Guess I should probably do one--need to pick up extra plugs. I've just been reading the plug after shutting down at idle.

Do you have a sump spacer on that g5?

No sump spacer. I was thinking about one or possibly an external oil filter sump as an upgrade. Is it more important to install one than I thought?

No airbox, by the way. Running a dual inlet K&N filter (MG2640).

I believe if you pull the carb and intake stub you can see the intake valve? Take a look with a bright light, compare both sides, is the back of one valve, or both, oil covered ?

That's a good idea, should be easy enough to do. Will take a look soon.

[lucian]

A friend with a t3 had constant oil puking into his air box and smoking out the exhaust as a result. It all went away after he installed a sump extender. Plus no more dropping the sump for filter changes, win win.

[pete roper]

Once the capacity is taken out over 850 the breather system often struggles to cope with the crankcase pressurisation unless an extension is added. The extension isn't there to allow the carriage of more oil but to increase the internal volume of the case and reduce the pumping action of the pistons.

Given the circumstances though I'd think maybe the second ring is upside down or one of the guides is loose. We're the guides replaced or were k-lines inserted?

Pete

[Antiquar]

The guides were replaced, no k-lines.

I'm pretty sure the rings were installed correctly, but that wouldn't be the first mistake I've ever made.

[pete roper]

Stepped ring should be in the middle groove. It's a torsional taper faced semi scraper and should be installed with the step facing down. It is sometimes mistaken for a ridge-hunter and installed in the top groove with the step facing up. If this is done it will pump oil into the combustion chamber.

If the guides have been replaced, something I'd never do unless one was loose in the head, then there is the risk that it has been installed with insufficient interference and may of come loose or installed the wrong way.

Pete

[Antiquar]

Thanks for the information Pete. Didn't know that about the guides, will keep that in mind. If they do get loose do you suggest k-lining or replacement? Also, how much smoke would you expect with the scraper upside down?


I pulled the carbs/manifolds off the heads today to get a look at my intake valves. They look more cruded up than I'd expect for the miles since rebuild, but both sides were consistent and smelled like fuel rather than engine oil.

Left side:


Right side:


I went for a 50 mile ride this morning and, once again, the smoke stopped a few minutes into my ride. Got a few drops of oil from the breather line after parking. No real drama. I'm starting to think I'm chasing my tail over this and should just put some more miles on the damn thing.

[twowings]

If your oil level isn't at the top mark, add a couple of shots of Marvel Mystery Oil and take her on a long afternoon ride...