im building a mini copper from some scedule 40 pipe i had laying around its only going to have one bottom pipe. 20in bike tire for front and snowmobile tire for back using a 5hp briggs with a 1in shaft for the engine and using a comet 1in bore clutch 10 tooth 40-41 chain cent. clutchs. and a 60 tooth or 72 rear sproket not quite sure of rear tire size but looking to get at least 35 out of it. sorry for the crude pic but this is what going for.