My super Sherpa has been running very well but twice now when I have drove to work it hasn´t wanted to start. It sounds like a car trying to start but it just won´t. The batterie is good. The last time it wouldn´t start I took out the batterie, cleaned it out and it worked just fine for the last two weeks. The only things that are different from driving it to work is that it´s only a mile away and normally I drive it a lot farther, and I use the handle bar lock. Please Help!!!