If it does it in all the ranges, check your forward/back pedal first. Unless Kioti changed the design, these pedals where known to bend. Mine did the same and after checking, I found that the pedal would hit the floor/foot rest before the actual drive linkage, under the foot rest, was through all its travel. I just bent mine back and all was fine. Some members have posted reinforceing this pedal by welding on a steel square bar. The ranges are all geared, so if it's slower in medium, it should be slower in the other ranges too.