i have a 400ex with pro meg exhaust full system.... i noticed after riding that there are black spots on my engine that easily wipe off but i noticed that it comes from where the head pipe connects to the tail pipe.... i cranked the quad up after noticing this and i can feel a lil air coming through this area so its spitting someting out through here what is the problem.... the clamp that holds the two pipes together is in the right place and i dont see how to keep the air froming coming through this part i mean there are little rivets in the pipe where it connects and thats where the air is coming through..... if u reply to this and if u think this is a problem leave your email address and ill send u a picture of what exactly im talking about.... thanx

 

you should try taking the pipe/head pipe off and looking at where it conect to the engine and make shure its not bent/not lined up/cracked and make shure nuthings clogging it and wehn you put it back on make sure it is on realy tight or it will leak air hope this helped

 

Put some high temp silicone on it.

 

Same thing happened with mine.Saw the black carbon blowout on my rear shock and motor.Pull apart, clean up pipe and silencer with solvent to get carbon off and put some high temp silicone on end.slide back together and tighten clamp.No more leak.