My bike is still smoking, a lot especially on first startup. It acts like a bad valve seal. They were new. Has anyone ever had a new one go bad? Hope I did not brake an oil ring.
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1981 with BBK Status
- Thread starter BowlingSS
- Start date
As a rule.... valve seals smoke more at idle and on decel. Oil rings smoke all the time.
Thanks Jim. At least my 72 and 73 did not smoke after rebuilding.
Loose valve guides cane also cause similar problems.
After the bikes gets warm hardly no smoke. Almost all smoke comes after setting overnight. Valve guide or seal must be bad. Think I will wait before I remove the engine. It sure does run strong. A lot stronger than my 72 or 73.
Does the smoke come from one exhaust pipe or both?
Does the smoke come from one exhaust pipe or both?
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Does it smoke more when you first start it or after it's warmed up?. As Jim was getting at does it smoke more on decel or when accelerating?
Never mind reread your posts. I think I would replace the valve guide seals. It is possible to do with the engine in frame. When doing see if the valve stems fell loose.
What brand of valve seals did you use?
same as the other motors you built??
it’s not unheard of to get bum seal.
same as the other motors you built??
it’s not unheard of to get bum seal.
Most of the time I use the ones in the gasket set.
For what it's worth....I just installed my BBK kit on my 74 after having rebuilt the engine last year. So new rebuild, one riding season/~2500 miles on it or so. When I pulled the motor apart the piston and valve faces were pretty gnarly on one side and the likely culprit seemed like a bum valve stem seal. I installed the ones from an Athena set. What's weird is I never really had any issues with smoking. But it was hard to argue with what was on the piston as you can see below (original post here). You could have eaten off them when I installed them a year ago. So, not unheard of I guess.
I guess I need to removed the muffler to see which pipe is smoking.
I removed the engine today and found one of the bottom thin oil ring was messed up. I made the mistake. My ring compressor has never failed me until now. I am glad it was not one I am selling. Valve seals look good. They are the blue seals. Had to order a sets of rings and also both cam shaft seals were leaking. I replaced them with ones from xs650direct.com. I also ordered another set.
Running great now that I replaced the rings. No smoke at all.
