Troybilt mower suddenly won't go fast
I have a Troybilt (MTD) riding mower model 13AZ609H063. A week ago my daughter was mowing and suddenly it wouldn't go forward. I found that the spring holding the idler pulley at the transmission had broken/fallen off. While I waited for the part, I simply used string and strong rubber bands :-) to keep tension on the pulley and she was able to mow fine. Once the spring arrived I installed it and now you can push the drive pedal about as hard as you can and you move along a slow pace - simply can't go any fast and can't push the pedal any harder. This is a variable drive (I guess that's the right term) with just forward/neutral/reverse and the speed comes from how far you push the drive pedal. I've looked underneath the mower and the pedal seems to be doing what it's supposed to do - tightening the whole drive belt system so that power transfers from the engine pulley to the transmission pulley in the back. Seems like the new spring is too strong and not allowing the belt at the engine pulley to get tight enough but that's just a guess. Any suggestions?