Ok, here's what happened. I've got a '78 pa50 it was only getting a top speed of 17 down hill when I bought it. I put on the 60cc stocko shocko cleaned up the reed block put a new Chinese carb on n was getting 22mph on the flat. I got greedy n wanted more. So I order a paII reed took the old carb, bored it out to half inch n put the 78 jet from a paII carb in it. The thing idled at max speed. Couldn't get it down to a spot where it wouldn't rip out from under me when I put the stand down. So I put on the Chinese carb with the paII block n I it bogged way down to almost no power. So I ended up going back to the Chinese carb I had with paI reed block and thought all would be well. I would b back to 22 mph. Not so much. Top speed is 17 on the flat. Only thing I didn't mention is I ground down the aluminum tab on reed block n put in a metronik reed block gasket. Any ideas why I lost so much power???