I think my 400ex is running a little rich it is puffing black smoke. Which jet do I change, the slow jet or the main jet, or both. Thanks for the help.

 

Would it help if I just put a few more plates in my exhaust to lean it up?

 

i'm not to firmilar w/ supertrap pipes so i'm not sure about the plates. what size jet is in it now(main jet) and what performance mods do you have other than that if any?

 

I think its a 152 main jet I have a K&N power kit and the supertrapp with 10 plates

 

Adding more plates (discs) to the tail will lean it some...the reason for the discs are to "fine tune" your tail to the engines liking. Check your plug to see if its all black and nasty, if so, install the stock 148 main. A simple test would be to remove all the discs and run it to see if it's still over-rich....before changing the main. Not to sound stupid, but make sure the air cleaner is in top shape and not all stuffed up with dirt.

 

Thanks for the info, I'll give that a try, My spark plug was all black and nasty. I just cleaned the air filter about a week ago.