When the "Bikes with motors" section was first built, there were only a few people building these MOTORCYCLES. Only two of us were using the 4-stroke Briggs style engines on here, and Cobrafreak once he figured out the little Chinese engines were junk. When the pedals don't propel the bicycle, it's a motorcycle. Not a moped, not a bicycle. These are no longer the basic, light duty Chinese kits that will work on a bicycle for a short period of time. I suggest everyone build a bike with a Chinese kit for practice. PLEASE remember that a 3 hp Briggs style engine is a totally different beast than the little Chinese engines. Anything over a 3hp engine is beyond overkill for one of these. Even with a 3hp engine, bicycle tubing is rarely up to the task of handling this. They are heavier, have more torque, vibrate more, will go faster, and will need a lot of braking power. Adding suspension in the front or rear without knowing what you are doing is very dangerous. Using low pressure tires on cheap rims is dangerous. These engines, when properly geared can reach 40-50 mph. Cheap tires can come off the rims. Which brings me to wheels. You want good quality rims, with HIGH QUALITY hubs. Spoke gauge is up to you. I understand that Briggs style engines are cheaper and easier to come by, but it does not mean the build will be cheaper. In fact, it's going to cost you far more to have a safe, reliable motorcycle. Oh and always wear you safety glasses. Feel free to add to this, or make me look like an a-hole.