We are moding an atc 70 to race flat track locally and want to replace the rear axle sprocket assembly with one from another atc/atv to be able to run smaller sprockets. The atc 70 assembly can not be modified to run smaller sprockets. The axle spline looks like it is 29 spline. If another atv has the same spline count We could start with it and machine it to work. We are running 11 inch kart tires.