Shorter intake tube = higher rpm

The RPM limit is due to the design of the engine, there are some engines out there that have no intake runner and the engine would run better, just because of the restriction it causes, but I think there would not much increase in RPM. A 3rd mounting point is a good idea, most motorcycles use 3 and 4. I saw one bike with a turnbuckle from the top of the engine to the upper frame and he could adjust the tension. I would like to make one that would pick up the top head bolts and a nice bracket to go up to the frame. These engines use the torque and not the higher RPM"s. I change the ports and get the most out of the engine and then gear it up. I have a 39 tooth sprocket and it will still climb amazing hills and go over 35mph. Have fun, Dave