I need help with the model of tecumseh engine that will fit this bike. The guy I bought it from included a sears roto spader with a 6hp tecumseh engine. The engine has a 1 inch crank, I was going to turn the crank down to 3/4" but found out when I mocked the engine up that there is no way the clutch would line up with the rear sprockets. This is the 2 speed roper bike with 3 chains. I have the correct clutch but am having a hard time finding a good engine for it. A briggs would work if I install a bowl carb on it. Anyone know what the biggest tecumseh engine would be that would bolt in and allow everything to line up?