The XR50 now has a 88cc kit, It is twisting the tire and tube, so the tube gets torn and gets a flat. Are there rims like on full size bikes that will keep the tire and tube from twisting?
wondering what air pressure you are running. Our cobra's run HIGH Hp even above that of the 88kit...Maybe an effect of torque though? I'd duess 20psi or above is where you should be. I have seen guys drill the rim and install sheet metal screws in to the bead to keep them from spinning but that was on the 70's bultaco's...
Had the same problem with my son's KLX 110, so I installed a rim lock. The rim was already pre-drilled. Just don't buy a Kawasaki rim lock unless you want some serious sticker shock :) I believe the smallest available is a 1.6".