A direct drive system can be a chain driven system or friction drive
system, how they work differs completely. Friction drive means engine
rides on top of your tire.
A bicycle needs to be pedaled for some distance, (¼ of a block) to reach
15 m.p.h. before a lever can be engaged to compress the drive roller
against the tire which starts up the motor, at the same time, twisting the
gas throttle to accelerate so as to avoid the engine from stalling.
Note: This is a crude method of starting the motor, since, it requires
leg and arm strengths, reflex and the ability to do all that at once
control of the bicycle.
Furthermore, this balancing act is done each and every time one comes
to a stop.
CHAIN DRIVE SYSTEM
As a bicycle is pedaled for a distance (1/4 of a block), the chain
attached to the wheels’ sprocket turns the engine sprocket to start the
engine. Although, less complicated than the hand lever type, it has its
own serious flaws.
Often these engine kits are sold with sprockets that bolt onto the spokes
of the rear wheel. Any cyclist that has ridden a bicycle knows that spokes
break or loosen and rims bend, therefore, a sprocket attached to either
will fail sooner or later.
If the chain falls off the sprocket, jams into the spokes or loosens and
slaps any body part: leg, back, neck or head, serious injury or death
If a flat tire occurs, it will cause one hell of a problem changing the
tube and aligning the wheel sprocket and motor sprocket. (An expensive
process to fix.)