My question to you all is do you think that it would be ok to just add a XR 400 cam to my 400. all that I have for an upgrade is a full LRD exahust and a UNI Filter. Will it run wierd without haveing a port job and a higher compression piston, or will it run fine. thanks-
Eddie

 

It will run fine, just like an XR dirtbike....

It will slightly shift the power more up into the mid and upper mid..

Don't expect any big differences with only this change.

 

While your in the engine I would put in a 10:5:1 piston or a 11:1. With these two combos it will feel like a completely different bike. The 400EX works well on higher compression piston.