I own a 400ex. I have a Double Barrell pipe with a 156 main jet. I am scheduled to get a new Raptor because I don't like getting beat. However, my friend picked up his new Raptor this weekend and I may stick with my 400. I lose power every time I take it to the dunes. I have a K&N, precharger, and run with the lid off. I was wondering if anyone knew what I should try so I don't have to make the dreaded switch to a Yamaha. Thanks.

 

Are you getting any sand into the engine? You shouldn't be losing any power after a trip to the dunes... I have been a few times, and run the bike extremely hard, it still outruns friends bikes that are newer and haven't been to the dunes...

Also, you are probably at around the same altitude as me (anywhere from 700ft to 1200 or so), I run with stock exhaust and a modified air box lid, a 165 main develops the fastest ET's in the straight drag on my bike, you may still be lean...

What didn't you like about the Raptor?

 

Engines really do change power output from climate changes. Hot summer days kill power. On a cool fall day, everything has more power. It has to do with the amount of oxygen available to aid in combustion. On different days, engine performance will change. I say jump on the raptor bandwaggon if that is the kind of quad you really want. If you just want to beat him stick with the old 2 strokes, they ALWAYS win.