Next Modification?

I have a 2000 400ex, and the only thing I have done to my quad is put on a K&N air filter, with pre filter, no air box lid, no snorkel, yoshimura slipe on and re jetted the main to a 165. What modifications should I make next, to gain more ponies. I'm looking for more top-end power, I have plenty of low-end. and how much should expect to spend on my 400ex? Thanks and I can't wait for the advice.

[Guy400]

You could remove the head pipe and take a die grinder to the sloppy welds around the flange on the inside of the pipe. Free mod unless you have to buy a grinder.

Does grinding these welds give a noticeable boost?
JOhn

[Guy400]

I wouldn't say noticeable in and of itself. Anytime you remove some of the restriction in the exhaust you help out the top end. More than anything this mod is free and will help out when higher compression pistons or cams are installed.

[Tommy 17]

U can buy a xr400 cam 120$ and a stock bore je 10.8:1 piston for 150$ these will do a lot for u. u may also want to get some porting done. a slip on pipe will do some for ya 2.

If i go with the xr400 cam and port and polish then how much would I spend all together, parts and labor?

[FlyinRed]

Cam's 120 or so. Porting seams to be arround 150-300 depending on play to race. Of course that's not including Remove&Reinstallation.

[Wheelie]

Try stepping down a size or two on the main jet, and go up one size on the pilot jet. If you are running too rich, the top end power will suffer greatly. Try a 160 and see how it runs. If the top end is improved, try a 158 and so on. Play with the jetting until you get the best seat of the pants feel. Good Luck