I have a 110cc Honda clone engine I was trying to get going. It was having the same symptoms as another I had that the one way clutch on the flywheel was bad. I replaced the flywheel/one way clutch with another I had. I had the rear jacked up off the floor and when I started it I swear the wheels were turning in reverse! This engine doesn't have reverse. It only ran for a couple seconds on the squirt of gas I put in. After that it always went forward and now it's back up and riding. Was I seeing things or could this have happened?

 

If the rear wheels are not perfectly balanced, when free to rotate, they will turn backwards or forwards until the heavy spot gets to the bottom. This usually happens when you lift it off the floor, but when you start up and things start to vibrate, sometimes this frees the axle enough for this to occur. Vibration itself can cause "precession" which is why nuts can slacken until they come right off the bolt, if left "finger tight"