Ok I blew up my gt5 with about 450 miles on it. The motor did run strong. I know it was my fault by over reving it on accident. Pot hole with clutch in trying to rev match going 25mph. Needed a new motor so I called Duane. I thought that the price was a little steep, until I got the motor. There is a reason he charges a little more for the little china girl. I have about 75 miles on this motor now so its not even broken in. It will out pull my gt5 broken in. I have more low end torqe and my top end is at least the same, possibly 1-2mph higher. The ports looked a lot cleaner and the gaskets that came with the kit are a LOT better. It almost looks like he cleaned the ports up. The kit comes with a straight head as opposed to a slant head. The straight head seems to be a bit quieter than the slant. Duane claims to have a 69cc engine over a 66cc...although I cant prove this. All I am saying is that if you dont want to fiddle with a china girl out of the box then spend the little extra and get the F-80 from thatsdax.com over the Grubee GT-5. Thanks for reading this little review of mine. Also thank you Duane for making top notch stuff.