Ever seen puffs of smoke in the petcock vacuum line?

[GreasyC]

My friend has an XS750 triple. He's having problems with it and I helped him do all the usual checks. Compression and leakdown tests were good, spark is good, timing is good, but one odd thing I saw was that in one of the vacuum lines that go to the petcocks there appears to be puffs of smoke pulsing through it in time with the engine. Can't say for sure it's smoke and not fuel or something but whatever it is, it shouldn't be there right? The left side line doesn't have anything like that going on.

Have you seen that before or know what it is?

 

[TwoJugs]

Sounds like a break in the hose and some of the crankcase fumes are getting out there? If uit is that bad it might not have enough vacuum to hold the valve open, low or no fuel flow?

 

[Underdog]

x2 or the petcock needs rebuild

 

[TwoJugs]

I had one of mine empty the fuel tank into the crankcase through the vacuum hose. It ran bad and smoked like a worn out 2 stroke. Lucky thats all that happened until I figured it out. I rebuilt mine and they didn't last 6 months with the lousy chinese rubber they use now. Might be better off getting the non vacuum set if that ends up being the issue altough they probably use the same chinese rubber too...