Originally Posted by happyvalley
...Then, define reliable ...
More reliable engines, take it up a notch.
Heavy duty wheels, up a notch.
Jackshafts, again up.
Weld your own frames? Take it up a bunch.
Do your own due diligence and but ask any knowledgeable bike mechanic/MB builder about what it's going to cost to produce a from scratch, frame, drive train and suitable components equipped MB, built for mass consumer reliability and you will have entered or even surpassed the scooter/small motorcycle price point.
Yea, that is the thing.
Stronger, more reliable parts == more weight, until you have a vehicle that's so heavy that nobody would pedal it anywhere even if it had pedals.
So, get rid of the pedals, and what's left?
The chinese scooters, that's what.
The motorized bikes are fun to hack around on as a hobby, but (as a few people have tried and found out) you cannot build one cheap and expect it to run very long. And the more-expensive motorized-bike setups cost way more than the Chinese 50cc scooters.