I have a sachs wich seems to be loosing power as I ride. It will be running great, and then seem to loose power. I will try to start it back up when it is still rolling, but it wont. I will let it sit for a min or so and then it will start right back up and run fine, until it decides to start to loose power again. Any suggestions? It seems to feel like a gas problem, but there is plenty of gas and air, correctly mixed. Also, It did backfire on me one time while trying to start it after one of these "power outs" Is this a timing issue?