Smoke... Valve guide or ring???

rule62 · April 30, 2009, 11:59:05 PM

I've just noticed a little bit of smoke coming from the exhaust of my '04 620. It is definitely oil. It mostly happens when I am warming up my bike. It is standing still and the temp is under 170 degrees. I began to notice it after Dietrich and I performed a valve adjustment a few weeks ago. In order to figure out which cylinder it was coming from, I first checked the plugs. They both looked practically brand new. (I just installed them a few thousand miles ago.) No discernable difference between them. I was expecting one of them to show signs of burning oil. Next, I removed the little bungs on the exhaust and ran the engine for a bit. Based on this experiment, the smoke seems to be coming from the vertical cylinder.

There are a few factors I can think of. I am hoping that others might chime in with their experience.

1. Is it possible or probable that we may have nicked a valve guide when adjusting the valves, which is allowing oil to get into the top of the cylinder?

2. If it were a piston ring, I expect that I would feel a loss of power. I do not. The bike seems to pull just fine. A compression test would tell for sure, but wouldn't the good old "butt-dyno" register a bad piston ring?

3. After installing a working oil-cooler prototype (diverter spring and all) I believe we may have overfilled the oil. I've let some oil out, but ran the bike just after, and it still smoked.

4. When the bike is fully hot (200+ degrees) and has been ridden, there is little or no noticeable smoke.

I'm gonna get back into the vertical valve-head and see if anything is awry. Are there an other tips or experiences you can share that may help diagnose my smokiness?

Thanks,
rule62

PS: My oil looks like shit. I know it needs to be changed, but would seriously shitty oil cause smoke if there wasn't anything actually wrong?

Ddan · May 01, 2009, 04:07:07 AM

Off the top of my uneducated head:

How many miles on the bike? I'm told you can go a long time on fairly worn valve guides before it becomes an issue. How did you determine " it's definitely oil"? It's normal for the bike to produce some smoke/vapor as it's warming up.

1: You could have nicked a valve seal, unlikely you damaged a guide.

2: I'd be really surprised if you could feel a loss of power from a ring that's just started going.

3: How much extra oil did you put in?

4: See my first comment.

My opinion, change your oil and run it. YMMV and wiser minds may disagree.

Howie · May 01, 2009, 06:54:37 AM

Rings usually cause smoke under load, guides usually cause smoke on deceleration and acceleration after idling as well as start up. An engine can use oil due to rings with good compression. Do check the crankcase breather, a clogged breather can cause oil consumption. Yes, contaminated oil or oil that has lost it's viscosity can be your problem.

Norm · May 01, 2009, 07:51:43 AM

Sounds like rings to me. Do a leak down test.

rule62 · May 01, 2009, 11:02:56 AM

Thanks.

The bike has a little over 14K miles.
I think I may have meant valve seals in my original post.
My crank case breather is capped with a small filter. it no longer routes back to the airbox.
Overfilled to the point that when the bike was upright, oil totally filled sight-glass. I let enough out that now it sits between the lines when upright and cold.

It's weird that it only smokes when idling and somewhat cold. It just began after servicing the valves. That's why I suspect that we may have botched something.

I've never replaced a piston ring before. I imagine it's a pregnant dog.

Howie · May 01, 2009, 08:48:43 PM

Are you sure the smoke you are seeing is not water vapor (normal)?

Norm · May 02, 2009, 06:35:29 AM

Rings seat better as they get hotter. The leakdown test will take the guess work out of it. No, i't not difficult to install rings, just be careful with the oil ring. I suspect that by the time you pay dealer prices for OEM rings, you might as well put some nice aftermarket pistons in.

Langanobob · May 02, 2009, 10:30:21 AM

+1 on what Howie said and don't start tearing it apart until you've done the leakdown test or otherwise absolutely confirmed that you do have a ring or valve guide problem.

I have a lot of hard earned experience at misdiagnosing mechanical problems and taking things apart that aren't broken

rule62 · May 03, 2009, 12:42:05 AM

Definite that it is not water vapor. Gonna do a compression / leak down test as soon as I get my hands on the right tool. Still leaning toward something on the valve side of things due to the smoke appearing only after we messed with the valves. Are OEM rings really that expensive that I should consider replacing the entire piston?

Thanks for all of the input. Please keep it coming. I'll keep you up to date with my discoveries.

ducpainter · May 03, 2009, 06:52:36 AM

Quote from: rule62 on May 03, 2009, 12:42:05 AM
Definite that it is not water vapor. Gonna do a compression / leak down test as soon as I get my hands on the right tool. Still leaning toward something on the valve side of things due to the smoke appearing only after we messed with the valves. Are OEM rings really that expensive that I should consider replacing the entire piston? Thanks for all of the input. Please keep it coming. I'll keep you up to date with my discoveries.

A drop in high comp kit (2 pistons and rings) for a 900 is $329 from ca-cycleworks

A single set (1 piston) of OEM rings is about $200

OT · May 03, 2009, 09:40:16 AM

Isn't there an oil drain in the base of the head (under the valves) - could that have become blocked during/after the valve adjustment?

ducpainter · May 03, 2009, 10:22:22 AM

Quote from: OT on May 03, 2009, 09:40:16 AM
Isn't there an oil drain in the base of the head (under the valves) - could that have become blocked during/after the valve adjustment?

If he left his 'plug' for the drain in there it could.

Ddan · May 03, 2009, 10:53:30 AM

Quote from: ducpainter on May 03, 2009, 10:22:22 AM
If he left his 'plug' for the drain in there it could.

If that were the case, he'd probably have a little more going on now than the possibility of a bit of smoke in the exhaust.

Howie · May 03, 2009, 11:16:46 AM

Quote from: DDDDan on May 03, 2009, 10:53:30 AM
If that were the case, he'd probably have a little more going on now than the possibility of a bit of smoke in the exhaust.

Worth a look, anyway. Back in my youth oil burning due to oil returns clogged from sludge was far from uncommon and too often the reason for unnecessary engine overhaul. If the return is not completely blocked there will still be some return. Anytime I block off something like that I tie string or wire around the object so I am less likely to forget it. Sorta like a string on a tampon.

rule62 · May 03, 2009, 12:34:53 PM

We tied a bit of safety-wire around the bolts we used to block the oil return gallies when we adjusted the valves. I'm sure we removed them before we buttoned everything up. Now you've got me thinking about going hi-comp for the fun of it, but that would probably mean fuel remapping, and I haven't got a PCIII. I'm gonna try to keep it simple.

Thanks again. I'm not sure if I've expressed my gratitude lately, about how much I appreciate this community. DMF FTW

It'll be a week or two before I get in to everything. <business trips> I'm gonna go the route of opening up the valve head to look for anything unusual we may have done while we were in there, and doing a good oil change first. Do you think a heavier weight oil might put a patch on things until I can accumulate the extra dough for the hi-comp set up?

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Smoke... Valve guide or ring???