I went to take the belt off of my sled yesterday and put the wrench in and started to tighten it up and the sheaves would not move. Do I have a problem or am I just going about it all wrong? Last winter on the last ride of the season, I fired it up burped the throttle to free the track and it took off on me! I hit the brake and the engine stalled. Then I opened the hood gave the belt a pull restarted it and everything was fine. Whats going on?