Well, I've got a stock-bore 11:1 compression piston, XR400 cam, FMF Power Core IV-2 silencer, Uni filter w/open airbox and a Dynojet kit installed.

Now, what do you all think I could do to get some more power from the motor? I'm not wanting to go back down into the engine right now. Maybe later on. Anyway, I was thinking maybe a good full exhaust system. I had looked at the Curtis Sparks X-6. Would the larger header actually help my motor out? I know that a larger head pipe on a stock motor does nothing, but what about on my motor?

Any input is greatly appreciated. Thanks.

 

i have a xr 400 cam 10:1 piston and a fmf megamxa silencer and a h flo header and a k&n filter plus a quicksilver carb if u get a mod got with the carb its is great lots more torque and top speed and throttle responce is second to none the hi flo header will help cuz the motor breathes more freely hope i helped

 

you could go for the sparks if you got the money, or get the powerbomb header

 

The White Bros. pro meg set-up should pick up a couple of hp's on your set-up....the P-core is fine in low-mid, but is'nt quite as powerful on top since it is a 2-stroke design....the Pro meg is a Rev-cone Meg (made for a thumper).

Also, the latest ATV sport mag have a test on the Edelblock carb...I believe it is 1.7 hp on a stock 400ex and 2.8 with the airbox lid removed....or maybe a FCR?

You could play with gearing.

Timing advance key maybe?

Have you dialed in the jetting perfect? There's cheap HP and TQ there.