Re: Hey, new guy here. Planning builds for 8 bikes on MTB frames. Recommend some pa
If you want something simple to operate and maintain that will run all day long (you mention 90 miles) with a pull start and automatic clutch 49cc 4-stroke.
It runs on regular gas and reliable.
Figure about 28MPH direct drive for the less speedy family members, and make a couple of jackshafted 3-speed shifters for those that need more versatility (climb hills, haul ass, or tow another bike).
That's what I would so if was a worrier like you ;-}