I changed from a centrifugal clutch to a torq-a-vertor. Made a world of difference. I have a 65 tooth rear gear on it now. I have a 60 and a 78 tooth also. The 78 tooth makes the chain ultra close to the ground. I'd like to try a 70 tooth to see how much more low end power and speed I get. The 60 tooth would definitely be for a long stretch run. I've modified the engine a bit. K&N air filter, re-jetted the carb, built my own header, removed the governor, cut off every other fin on the cooling blade. Every modification had made significantly noticeable power gains. Since this is an original Lifan, all the parts are 100 percent interchangeable with the Honda parts.