Waiting up for parts to convert to NuVinci hub, so I fixed what I have for now.
Last week, there was major vibration and wobble at the bottom bracket and shift kit location. I removed the freewheel mechanism, and sure enough, it had failed. While inspecting everything, I also detected a CRACK! on the 22-tooth bicycle chainring!! This 22t sprocket is actually a thin cassette cog. Couldn't find a replacement, so I ordered a SBP 24-tooth chainring. I just need to drill four bolt holes into it, since this sprocket is a 5-hole cog and I use a 4-hole freewheel mechanism in my shift kit. All gear ratios will rise a little, but no biggy.
FYI, I run a GP460 4.2hp engine with Scooterguy frame mount, shift kit and 8-speed road bike cassette. The Happy Time expansion pipe fits perfectly onto my upside-down engine. Its headpipe fits great between engine and 4-liter HT fuel tank. Power is awesome, and the bike performs like a small motorcycle.