I am mounting a standard Chinese 66cc engine on an Iron Horse mountain bike with steel frame and noticed that the seat tube is slightly larger than the mount. I was wondering if this would cause stress cracks to the mount and is there anything I could use to fill the gap?
What I've done is find a tube as close to your seat tube, wrap with sandpaper and sand the mount down till it flushes out. Another way I've done it is to go buy a 3/4" copper fitting/union, and split it lengthwise then start cutting to take up the space.
I had the same problem with my bike. When I filed the mount to fit the bigger seat tube the mount lasted about an hour before it broke and then I had a huge amount of vibration for about thirty seconds and then the motor housing broke! I had to replace my engine. Lucky for me I bought I new one on sale when It was rumored that you could no longer inport them.
I got the sick bike parts oversized adapter. Its worked grate so far. I know that Is set up for the down tube, but its worked really good for my seat tube and I have not had any slippage so far. I have had over eleven hours on this motor with this set up.
