My polaris scrambler 400 starts and then dies after a few minutes. It starts to bog down and then dies. I thought it was fuel, so put on diffrent carb, new fuel lines, filter, and tried a diffrent tank. When the engine dies it locks up, i can rotate clutch back and forth several times and that loosens it up. I just had the lower end rebuilt with all new seals and bearings. If it locks up and I let it sit for awhile it will cool down and be fine. I really am stumped and need help.