your motor should have the keinen carb (sp) it was the one with a black plastic bowl.. it has the fuel pump built into the carb,,
the tank doesnt have a petcock,,, so , if gas is dripping , and its not the fuel line,, you have a crack in the tank... generally the carbs dont leak,, usually its the fuel line,, old and cracked leaking.
as for starting ,, the ignition modules used, a transistor, the grading process during manufacture was a little loose,, so the transistors many times dont kick in,, until as much as 2000 rpm is reached....that'd be about 10 mph, pedalling,,, I use a drill,, pneumatic,, but an electric,, variable speed works as well..... the flywheel nut,, may come undone,, now and again,, more often with electric,, i've found,,, but the flywheel generally doesnt go flying off or anything,,, so you can spin the motor,,, with the plug out,,, with the motor in the lifted position,,, grounding the sparkplgu against the motor. If you dont get spark,,, almost always,, i;ve found the fault to be between the plug wire, and the spark plug connector.. sometimes, if someone has had the wire loose,, and not put it back thru its little carrying sheath,, it'll get rubbed thru by the tire....
BHE,,, by the way,, was Bicycle Helper Motor , the motor was originally designed to be a ad on kit,,, to be marketed by Mccloch as a kit to be put on bicycles... the legal department got paranoia over the idea, and amf roadmaster built the bikes, in olney Illinois,, the motors being sent in from lake havasu arizona nearly 200,000 units