I bought my 400ex about 6 months ago, and looking to increase performance. Need some advise on which steps to take increase speed/performance without jeporadizing reliability.

 

I would suggest adding a slip-on silencer like white bros. e series, a uni, twin air, or white bros. air filter, and rejet the carb so it doesn't run lean(your dealer will do this). you also want to increase the flow into the airbox via vents or cracking air box lid. some people use k&n air filters but i wouldn't suggest them. they suck in dust particals that will grenade your new motor after a while. as described by white bros. that is the complete stage one power increase.

 

Thanks EXman. Took your advise, and installed the white brothers silencer tonight. Heading up to Dumont Dunes in two weeks, so hopefully i'll notice the difference. Carb and ignition next?

 

Make sure you're not running lean on jetting with the new pipe and all should be well.above all, have fun and let those bahshee guys see red ahead and hear the sweet, thumping melody of a well tuned honda machine!!!

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Another easy mod is to install a redesigned CDI box from White Bros. that moves the rev limiter on this quad. It lets you wind the engine out more without running into the limiter like many people do while riding.

Lightninn