How many teeth should my sprocket have?

[Sambino]

I've got a chopper bike, solid build, looks pretty nice, but the back wheel is only 20 inches in diameter. I've got a 80cc engine coming in the mail tomorrow, and I'd like to know if anyone knows how many teeth I should look for on eBay (with a wheel this small, a 44t is going to be much too large) for a replacement.
The bike is about 25 pounds, and I'm 130. There are some medium sized hills here, but nothing too huge.
If anyone has experience with small tires, and knows what might work best, that would be great.
Thanks,
Sam

 

[The_Aleman]

With a 20" tire and 44T sprocket, you'll be going ~20MPH @ 6000RPM. 26" tire would be going ~26MPH @ 6000RPM with same sprocket.

You would need a 34T sprocket to have same gearing as 26" with 44T. If you want to go 30 @ 6000RPM, you need a 30T sprocket. Every tooth smaller is worth roughly 1MPH.

 

[Sambino]

What is this?

This came in my kit, and I have no idea what it is. Aside from the chain (I'm waiting on a longer one, since I have a "chopper" bike) everything seems to be put together... but I have no idea what to do with this, or even what it is...
Is this an extra piece, or am I missing something?

 

[DaveC]

That part goes on the end of the clutch cable, kind of a safety stop. I use the threaded hole in the arm as well. The 49cc I just got doesn't have a setscrew, just that little collar but it has a machined place for that little nubbin to fit in.

One thing I did no one else does or so I've observed is I spread solder up and down the cable to make it tougher and less likely to get cut with the setscrew. Also, grease the cable, operates smoother and makes the cable last longer.