You can only take it up to so much and it still be reliable... see my other post. There are a few on here w/ highly modded warriors and they say they can keep up w/ the STOCK rappys. Once you start modding them too much past low-compression 450cc the oil pumps give way, I suggest picking up a used shee. Put it this way:

1500-2000$ motor work to warrior (to keep up w/ stock rappy)

2500$ (for selling warrior if its in good shape) + that 1500$= 4000$!!!

You can get a CHERRY shee for that price or a slightly modded 400ex.

Its your call.

Mike