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Oil in exhaust?

Field

CB750 Enthusiast
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I just had a valve job done by a very competent man. He also synced the carbs and tuned them. Cam chains were tensioned properly (while engine is warm). He found that one spark plug wasn't seated right because of tiny debris, fixed that.

But for some reason I still get some, and he isn't sure why. It runs nice. I get a little bit more of a poppy sound out of my left exhaust though. It might be some build up on the sparkplug that is going to go away, from before, but maybe it is causing the oil.

It is possible the oil is from inside the exhaust tube, but still how'd it get there?

There doesn't appear to be a problem with the valve guides that is apparant. Number 4 was a little tight on shims, but was corrected.
 
Oil can get into the exhaust from valve guides, a leak in the head gasket, or past the rings. If it's passing through the cylinder the spark plug will turn very dark brown or black instead of light brown or white. (black can come from too much fuel too)
 
Hm the strangest part is still the perfect compression. Could compression change at higher RPM's?
 
When you say "Valve Job" do you mean the head was removed and disassembled, the valves and valve seats where recut and ground?

If yes, the head gasket and valve guide seals would've been replaced leaving only a worn, stuck, or cracked oil ring as a suspect.

If no, the good compression would eliminate the head gasket and leave the other two posibilites.

How much oil are you talking about?
 
No, the head wasn't removed.

It pooled up till there was around 1oz or so sitting at the end of the pipe. I'm sure a little bit fell off the back.
 
I'm watching to see if it does it much now that everything has been tuned up. The mechanic made it sound like it was.
 
The work you describe would not affect how oil would get in the exhaust.

If the bike runs fine, you don't have to constantly add oil, and your not having a visible smoke issue I wouldn't worry too much about it.

Get a buddy to follow you for awhile and watch your pipes for smoke while you go through all the modes, easy, mild, and hard acceleration & deceleration.
 
It always seems to me like the right exhaust has more of a popping sound past 3.5krpm. Really fast little pops.

Having someone follow me is a good idea. I'm not sure the bike makes the sound while sitting still.

I could only assume if something is different it may have something to do with the oil.

Could seafoam in the gas cause a similar thing if a cylinder was really dirty?
 
It may of had to do with the cylinder that wasn't firing right, for the pops. I've taken it on the freeway a little and the noise appears to be going away. The only mystery that possibly remains is the black tailpipe end.
 
Had to look "seafoam" up. Gasoline additives that claim to clean are crap, except some of the name brand injector cleaners used in modern car engines, don't use them in carburators, it just ruins the gas. That alone might make it misfire.

You didn't mention one cylinder wasn't firing right before the tune up. That cylinder, exhuast port, and primary pipe, may have some build up from running bad that will take time to burn off.
 
There are two ways oil can get into the cylinder and burn:

1 - seeping down from the head (leaky valve guide seals, head must be removed to correct this)
2 - oil slipping by the piston rings (head and jugs must be removed to correct this)

If you're going to remove the head to correct the problem, I would go ahead and replace the rings while you're in there.

just my .02.
 
from what the OP said, he had a valve adjustment done (which will not correct any of the issues causing oil to be burned in the cylinder). a proper valve job (i.e. removing the head, getting the valves and seats recut and ground, replacing any gaskets that are removed or exposed as a result of removing the head, and replacing the valve seals) will stop any leaks from the top. while the head is off of the engine, you should probably replace all of the piston rings also. I should mention that the head cannot be removed with the engine in the bike.
 
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