They're good, and fast!
Other people have used doscycles, and I'm forgetting another.
Don't use 77 mopeds. Most people have had nothing but problems.
Is your bike running well stock? Pul-eeze do that first! It will save you lots of headaches. You'll need to be able to troubleshooting along the way, and it's easier to do if the bike is running well before you start slapping performance parts on.