I installed a tb 146 high comp with a lifan head and a cam a few days ago. I was racing it yesterday and every time on the back strait when me or my partner let off the gas, we would get smoke coming out of the crank breather. On one of the pits, I checked the oil and the level was fine, but a little smoke would come out of there too. We kept running it because the motor kicked serious ass, but then we ran something over that blew my back tire. I rode it back to the truck 2 hours later and I was getting a knocking sound when I revved the engine hard. I got home last night, warmed it up, drained the oil (had some metallic sparkle but nothing big), then adjusted my valves which were a little loose but not enough to make the knocking noise. I put the compression tester on it and with the throttle open, I was at about 150 pounds. My plug was beautiful so I don't think anything is burning up. I need to put some good bike oil in this instead of the car oil I had in it before, but I can't seem to figure out the strange knocking. My options right now are my head gasket is leaking, there's maybe too much slack in the cam chain, or maybe a bearing somewhere in the top end. What do you think? If my problems persist with a couple changes of good oil, I will take a video.