Tough PROFESSIONAL question By blitztek (Read 491 times)

[blitztek]

I am chasing a problem...

150cc Mishi Venice same as eagle milano, piece biella etc

2800 miles on it and it popped from the exhaust and would starve for fuel (closing petcock).

I adjusted the valves, the exhaust was tight like usual. set it to .004.
it also stumbled when accelerating, so I cleaned the carb, now when I start it, it runs really great, until it warms up. Then it still runs great but backfires from the tailpipe. sounds like a shotgun. Runs like a champ though.

I have checked the cam timing, it's good. I have changed the cdi. I have did a leakdown test on it and it holds perfect at tdc with VERY LITTLE crankcase leak (rings) I can't feel the air it's so small, I can just hear it.

i am stumped. what would make it backfire like this?

[terrilee]

small cracks at intake manifold ?

[alleyoop]

Sounds like you have a LEAK someplace, have you checked the Flange where it connects to the motor or you have a crack in the pipe. I would think if it was leaking around the carb area it would have problems idleing and bogging when giving it gas.
Alleyoop

[blitztek]

the gasket under the intake under the plastic sucked. I took it off, lapped the plastic spacer flat again (they always have a little warp to them) glued it last night before leaving the shop, now waiting for my associate to get back so I can take it for a test ride and not have to close the shop. intake is great, checked vacuum leaks, unhooked the emission valve junk to see if maybe it had a leaky diaphragm inside. We'll see...