I have a 2002 Walker MT with 20 hp. It has a speedup pulley on it. I have had trouble with the transmission belt slipping when I take off fast. I tried changing the belt and it didn't make a difference. I sprayed carb cleaner on the pulleys and blew off in case there was some grease on there. I am assuming that it is the transmission belt slipping. I guess it could be the belt from the motor to the jackshaft. I don't really know a way to tell which one is slipping. I had to replace the pulley on the motor shaft when the engine was rebuilt this winter because the old one broke taking it off. A note in the box said not to use a speedup kit with that pulley and provided a pulley to use on the jackshaft. However, there was a speedup kit used with the original pulley and it worked fine, so I left the speedup pulley on. I talked to the Walker Techncian and he said the speedup pulley could cause the transmissions to overspin, but if nothing had happened after almost 900 hours then it was probabaly not a problem. Anyone have any suggestions. Any help is appreciated.