Long story short, I acquired a Huffy "good vibrations" bike and a USED 66cc kit that was missing parts. The engine is in good shape, and upon inspection shows that the engine is well broken-in. Strong compression, starts without choke, and strong exhaust pulses too. The cylinder is shiny and the rings have worn the black coating off, so I'm calling them seated. Anyway, I get the bike assembled after ordering some parts (which includes a 41t sprocket) and I went for a ride. It starts up good, runs quiet, and pulls well without misfires. The only thing is that it's just incredibly slow! I thought for sure a 66cc with a 41t would outperform a 48cc with a 44t? I'm going to compare the ports on the 2 engine's and see what I come up with. Here's what I'm thinking: -put a degree wheel on the crankshaft -find TDC and make it 0* -note the angle at which the exhaust port opens -note the angle at which the exhaust port is fully open -same for intake opening and closing I also want to see if there's a difference between the two as far as magneto positioning. If everything check out, then I'll probably port the transfers where the cylinder meets the base. I kind of want to get to the bottom of why everyone is having different results with these engines. My 48 should not be powering past the 66 with a taller sprocket. Something's got to be amiss here. ... Something else I noticed is that this engine is a center-fire head. I haven't seen one of those in a long time. Then again, so is my 48 (but it's a freakin beast!) Maybe this is a much older model with bushings instead of roller bearings? I guess we'll see.