put 27" xtrs with 14" wheels on my 650 brute and the belt slips a little on take oft, what clutch spring would i need to put in there & will it void warrenty.

 

You probably need a stiffer secondary spring. The primary can only pinch the belt so hard before the secondary allows upshift......in other words the secondary ultimately controls overall belt tension. EPI or Dalton both have complete clutch kits spacifically for big tires or you can get the springs individual also.