just changed my jet

[Grant Casey]

well changed my jet today on my 400ex to a 152 main ,when i put it back together and when i started it up it was blowing alot of black smoke black why is this happing , and then i put my stock jet back in and it did then same thing

thanks grant

[Sjorge450R]

Originally posted by Grant Casey
well changed my jet today on my 400ex to a 152 main ,when i put it back together and when i started it up it was blowing alot of black smoke black why is this happing , and then i put my stock jet back in and it did then same thing

thanks grant

did you give it time to warm up??? My 300ex will smoke for a little when I start it up, but once it warms up, nothing smokes.

[bwamos]

Originally posted by Grant Casey
well changed my jet today on my 400ex to a 152 main ,when i put it back together and when i started it up it was blowing alot of black smoke black why is this happing , and then i put my stock jet back in and it did then same thing

thanks grant

Black smoke is from being too rich.

1) What did you do to warrant a jetting change? Was it necessary.

2) The main jet only controls 3/4 - Full throttle. If you started it up, and it was smoking while idlling, or under 50% throttle, a different part of the circuit is causing the rich condition.

3) If you loaded the engine up with excess fuel from the earlier rich condition, it may take a minute to burn off that excess fuel. Probably why you got black smoke when you restarted it again.

[bmurray]

why did you increase your main? you will only have to do that if you go with a better flowing air filter or a pipe.