My son has a 95 300ex that just started a problem, or at least I think it is a problem. I just put a Cobra exhaust system on, & rejetted the carb up to a 155 main jet. Now it cuts out at a much lower RPM than it used to. It sounds like it is up against the rev limiter, but if he short shifts it, it seems to do fine, but he really looses alot in the turns with this. My question, can this possibly be a problem with the CDI unit. I was considering purchasing an aftermarket CDI box with a higher RPM limiter. Or did I miss the mark on the main jet? It doesn't seem to be running rich, so I have set aside the possiblity of the main jet being too big. Any help with this will be greatly appreciated, thanks

 

I just realized I said I put a 155 main jet, sorry, it was a 135 main jet. Hope someone can direct me in the right direction on the problem.

 

There's nothing wrong with your cdi, it's just that Honda put an ungodly stingy low limit on the stock cdi rev limit.Your engine is now breathing better,and revving easier,so you are hitting the limit sooner, ran into the same problems on my son's, actually ran slower with the shorter tires and mods, putting a 14 tooth front sprocket in place of the 13 factory helps a lot, and is cheap. I ended up getting a modified cdi with the limit removed, so he can use all the power . Try a 14 tooth up front, should help a lot, and give him better top end to boot.

 

Thanks, for the advice, the 14 tooth sprocket will be on this week. I was hoping that there was nothing wrong with what I did. Thanks again

 

Is 135 main jet a keihin jet or dynojet?

 

It is a Klein, I tore the carb back down this evening, & switched the jet to a 130. After racing last night, & riding at the practice track a couple of hours today, I pulled the plug, it looks like it is running rich. I also will be going up to a 14 counter sprocket, & will see next weekend how it goes. Thanks

 

I am thinking the main for just a pipe is a 128, or with a filter. The 135 is a huge jump for that little engine. Our 300 is a 305 big bore and never went over a 132, before the 400ex carb. Oops did I just give up a huge secret?
The 35.5mm carb bolts right up.

 

The 400ex carb will work on the 300? Is it a direct replacement, or does the throttle cable have to be swithced?