400ex needs more high rpm power

[meanyellow03ex]

My 03 400 ex has the mods in the sig. It has tons of low and even more midrange power but seems to taper off as the revs climb. Is there any other mods I can do besides major engine work to improve the higher rpm power? Am I better running a full exhaust instead of the slip on? Maybe a rev box with a timing change? Any ideas?

[hardkoratvmxr]

well hmf is made for low-mid raneg power so that could be your problem right there

[Vista Cruiser]

HRC cam or copy with a rev box will make a huge improvement. The cam is a drop in affair that should only take you a couple of hours including the valve adjustment. I did that and geared it down one tooth in the front and man what a difference!

Good luck.

VC

[RiderTRX400ex]

yea cam, go with a hotcam, totally drop in and good gains...rev box too

since u want top id say get a stage 2?

[bwamos]

Agree.. the cam will help offset your power.
a top end cam will take some of your low end grunt and put it at the top of the rpms.

[meanyellow03ex]

Sounds like that may be the way to go. Do you have to upgrade rockers or anything else with a hotter cam?

[Vista Cruiser]

You don't hhave to upgrade your rockers if you stick with a drop-in cam such as the HRC or hotcam as mentioned above. Other, hard-welded cams, require the use of hard-welded rockers. Ask questions about this where you order your cam. You may want to get a service book as well before you open up your engine. It's really not that bad of a job though.

Also, you might think about a stock-bore high-compression pistion while you have the enigine apart. That way you will gain in the high RPMs without lossing power in the low range. The two together will make a very noticable improvement in speed and power.


VC