you have a bicycle (a mountain bike preferably. it's heavier and can put up with more. it's the horse of the bikes. complete with chain, gears, and hand brakes)
you want a motorcycle (an engine powered bicyclid with engine and associated parts and big thick body as sheilding from internal combustion and handbrakes)
easy enough. now this will be guided whereas evolution is not...
bicycle evolves randomly an assistor. i don't know if such a thing exists, but pretend it does. it makes the chain go faster than the pedal would ordinarily push it.
next step. the bicycle advances the assistor to a pedal powered engine. they're on all kinds of toys. natural precedence. they exist.
alright now. one to step three. the oops. a strain of the extra powered pedaled bicycle randomly grows extra sheathing in response to added wind. but it acts as a motion block and the bikes can't go anywhere. they all die.
another strain of bikes grows sheathing in response to the wind and is successful. this gives a bike with a slightly thicker body which is more aerodynamic.
so up to this point bikes feed on the energy produced by a rider's feet on the pedals. so one day a group of bikes are driving through an oil lake and decide that this is a much better fuel source so they buck their riders and come up with a crude combustion to run the engine instead of the pedals.
refine the engine, refine the body build to better withstand the strain of the engine and the wind and you have a motorcycle. with the original handbrakes.