I recently purchased one of the 66cc kits off of eBay and I must say that it's a really nice engine. I got it from user xjy19612013 who has sold over 1,000 of these and has a good rating. It came with the newer style tank and the newer magneto that doesn't have the white wire on it and I was surprised to see that it came with the clutch removal tool. I've read on here that the first thing to do is open these up and clean them out, but it kinda looked like it was already done; even the inside of the tank was spotless. I upgraded to 1/4 20 bolts and locknuts on the rear wheel sprocket because I didn't want it coming off and put red loc-tite on the studs and nuts, but not the head bolts. So far it has been a really nice running, easy to start engine. Being I messed up the hub on the wheel of my bike trying to get the brake arm off, I'm using a 24" instead of a 26" and it's still easy to start and I can get up to 30mph, but I don't want to hold it for long. I'm almost through the second gallon of gas running at 16:1 and when it's gone I'll go to either 32 or 40:1 and a different spark plug. So far, the only issues have been with the tank studs leaking, and the muffler fell off. It broke right where the pipe is welded to the muffler body, so since I can't weld and don't know of anyone that can, I went and bought another muffler on eBay and it should be here tomorrow. I've tried getting my fiancee to ride it, but she can't stand the thing. She said she wants it gone, but will let me use it until I find a job. I'm keeping it either way because of how much fun it is. I get looks all the time and today I talking with a guy at the bank who left on a quadricycle that had a Harbor Freight engine spinning a 34" airplane prop, which is something that I haven't seen before, but it did work. So, I've had my share of little problems, but this getting this kit is probably the best decision of the year so far. Next is to get a proper 26" wheel and go from the 44 tooth to a 36 and see what happens.
Out of all the things I've lost, I miss my mind the most.