Post by liftit on Jul 23, 2013 1:55:28 GMT -5
I'm facing a rather interesting situation.
From the beginning:
When stock, I ran a 70 main jet with the needle up one notchand it was rich enough to coat the piston and head with carbon. But there was no smoke in the exhaust
I installed a 72bbk recently and now it smokes like crazy at pretty much all throttle positions. At the same time, I get a popping noise from the exhaust when I lay off the throttle under load. So, I'm showing rich AND lean at the same time.
I've tried an 80,
, and 
jet. looks good. Still smokes and pops. Moved the needle up and down with every jet. Still smokes and pops. I've tuned the mix screw and the idle exactly like you're supposed to. Still smoke and popping.
Everything has been torn apart. Reeds are good, new cage gaskets installed with black rtv. New headgasket with copper gasket coating. Rubber ring style head installed with copper gasket coating. New exhaust crush gasket installed with copper liquid gasket and torqued as far as I think I can go without snapping a bolt.
Both me and a pro mechanic are confused. The only thing I can come up with is that I have bad crank seals (with no actual evidence of this) or somehow have an exhaust leak somewhere. Or my carb bowl isn't filling fast enough to get up to the pilot when I go from open throttle to closed.
A larger pilot might help the lean decel, but I can't find one that matches the look of my stock 40. I don't think a smaller main would be good because I'm borderline lean with the 80. I may drop the needle another clip.
Other than that, anyone had a similar situation?
From the beginning:
When stock, I ran a 70 main jet with the needle up one notchand it was rich enough to coat the piston and head with carbon. But there was no smoke in the exhaust
I installed a 72bbk recently and now it smokes like crazy at pretty much all throttle positions. At the same time, I get a popping noise from the exhaust when I lay off the throttle under load. So, I'm showing rich AND lean at the same time.
I've tried an 80,
, and 
jet. looks good. Still smokes and pops. Moved the needle up and down with every jet. Still smokes and pops. I've tuned the mix screw and the idle exactly like you're supposed to. Still smoke and popping.Everything has been torn apart. Reeds are good, new cage gaskets installed with black rtv. New headgasket with copper gasket coating. Rubber ring style head installed with copper gasket coating. New exhaust crush gasket installed with copper liquid gasket and torqued as far as I think I can go without snapping a bolt.
Both me and a pro mechanic are confused. The only thing I can come up with is that I have bad crank seals (with no actual evidence of this) or somehow have an exhaust leak somewhere. Or my carb bowl isn't filling fast enough to get up to the pilot when I go from open throttle to closed.
A larger pilot might help the lean decel, but I can't find one that matches the look of my stock 40. I don't think a smaller main would be good because I'm borderline lean with the 80. I may drop the needle another clip.
Other than that, anyone had a similar situation?
