Re: Newbie here
Here are important questions to consider when building for yourself or others:
1) What is the predominant riding terrain?
2) What type of physique does the primary rider have?
3) What will the rider's local laws allow them to have?
(Lookup and personally read these laws.)
4) What kind of bike is being motorized?
5) What is the bike to be used for?
6) How much of a budget is to be used for the build?
A Honda GXH 50 engine using a Staton 16.07:1 gearbox and crank drive system will give you the speeds you're looking for. Use a good mountain bike with front and seat post suspension with disk brakes.
Gearing: 22 T gear on gearbox to 44 T on the crank drive; crank gears 28 T, 34 T and 42 T; rear wheel gears 28-13 seven speed freewheel or cassette. This is how I would group the gears: uphill Crank 1 (28 T), wheel 1 (28 T), 2 (25 T) and 3 (22 T). Level ground: C 2 (34 T), W 3 (22 T), 4 (19 T) and 5 (17 T). Downhill C 3 (42 T), W 5 (17 T), 6 (15 T) and 7 (13 T). Uphill C1: W 1,2,3. Level ground C2: W 3,4,5. Downhill C3: W 3,2,1.
My bike auto shifts the gears on the wheel but you can use a similar setup. You can view my album by logging on to my profile. A tachometer will help with the shifting.
Seek the answers to these questions in order to get the most out of the bike you're building. We're here to help with any questions you may have. Good luck with your build.
Land Rider Jerry