engine smoking, should i tear into cylinder?

[dirtdawg]

my 300 is running great, i got a 138 main jet w/ a k&n air filter, cobra full exhaust, and airbox lid removed. but after revving and letting it run for about 2 minutes, it will smell really weird and will smoke like crazy. i think it may be the paint from the new exhaust, but the smoke comes out of the cylinder if i remove the carb from the boot. even the carb will smoke, but it isn't hot because it is the heat from the cylinder. i think that it most likely is a head gasket though, which may be the source of the smell. i just adjusted my valves today but it was doing the same thing yesterday. should i take the cylinder head off and check things out?

[300ex#996]

yeah rip the head off. usually smoking is the piston rings, and it does smell funky, so deffanitely check that out

[bwamos]

Smoke in the intake boot?

Was it whispy and white? If so that is partially vaporized fuel.

Only other way you are getting smoke in the intake is if your cam timing is way off and your getting blow-back.

Describe the smoking. Color of smoke, when it happens. High RPM, at startup.. after runnign for a while?

If it's after a bit of running and it's blackish in color, you're simply running too rich and there is no need to tear down the motor.


I'd wager with the 138 you're too rich. Probably need a 132 Keihin Jet with your mods unless you are at sea level.

Basically we need more detailed information regarding the "smoking" to help diagnose.

[dirtdawg]

it is a thin white smoke after revving it pretty high and letting it run, and repeating this for about 5-8 minutes. i brought it to my school's outdoor power workshop and the teacher said nothing was wrong with it. i'm gonna go with his opinion and that's it. it sounds good, runs good, and cools down very quickly. it might just be some oil i spilled on top of the engine a few weeks ago still burning off ad possibly the oil inside the brand-new exhaust to prevent the rusting that the factory puts in. i'm now running a 150 main and my elevation is about 150 feet above sea level. it runs like crap if you jet it too rich, and my quad does not run like crap at all. the exhaust has less than an hour of running time and smells weird because of the oil, so i'll run it once i get the other stuff squared away and see what happens. i'm also wondering if these machines run much hotter than a 250ex, because they have no oil cooler. i have a 250 and do work on it so i'm just curious. thanks.

[dirtdawg]

narrowed it down to the header pipe. i took it out for a ride today, the first with my new exhaust and valve adjustment and the paint was like chipping off on the header. the smoke comes right off the header-pipe and not the engine. it must be running hot but i have a 150 main jet, and stock is 122! the cylinder is very hot too only after about 10 minutes of riding. like i said before, i don't know how hot these are supposed to run. what should i do? i don't think it is the oil because i just changed it and put in a new filter. the rest of the engine is cold so it can't be the oil. Bad gas that's making my piston burn up? idk. please let me know before something bad could happen.

[asleepz]

a cobra is a pretty cheap system, probably just paint burning a bit.