Here's my little American Lifan. It has a iron jug lifan 140 on it with Mikuni vm24 exhaust and head work. This has a super small rear sprocket that needed the hub machined to clear the chain.
It's pretty happy at about 55 with some throttle to spare. I have grabbed the frame and tucked in before and had it well over 60.
Super scary at those speeds with the junk tires once they warm up really good.
