nitrorcr182

I am having a problem with the spur gear on my GT. It keeps stripping out, i dont think its the gear mesh. I recenty upgraded to a four shoe clutch and ive stripped 3 spurs inside of an hour. The slipper is losened all the way, so the only thing i can think of is getting a metal spur gear. Anyone have any ideas? or different ways to check gear mesh, other then the pice of paper between the clutch and the spur?