What are some changes you would do to make a 450 a better trail machine.

 

Flexx bars, razr 2's, and alot more.

 

Skidplates, especially one for the swinger. Switch out the thumb throttle or otherwise soften up the throttle pull. Add a nice slip on exhaust at least, one that is designed more for mx and low to mid range power output. That pretty much does it. the stock tires are actually pretty good for general trailriding, although they are susceptible to puncture like just about any 2ply tire will be.