I have just put a motor on my current ATB. A friend (stupidly) ordered a frame-mounted, chinese two-stroke motor for his high-tech, $1000 mountain bike with duel-suspension and a frame that could not in any way support an engine. So it's mine now
. Spend a few days taking it apart (I work on motorcycles as well) before doing the "conversion", and here are my observations-
The chinese two-strokes are very primitive. I'm surprised they have chokes, manual clutches and float-bowl carbs- the engineering and tolerances are from the era of direct drive belt clutches and spray carbs. Nonetheless, it is a damn simple motor and will run on just about anything as an oil (ran it in a test frame with and mix of gas and kerosine, gas and cooking oil, and gas and two-stroke oil and it did fine with all three). Good for a survival vehicle.
It came with a pullstarter, which I understand now to be aftermarket, but it works fine. Apparently they come stock with a bump starting system as the only way to start the engine, which sounds terrible- bicycle wheels, frames, the mounting studs on the motor, and the motor chain are not made to withstand the stress of constant bumpstarting. Anyway, I wired it up, put on the tank, etc. Didn't have to modify anything as I already have a light and toolkit. The supposed "locking" clutch lever does not work, so I drilled and tapped and place in the side of the lever where a bolt or screw could fit, enabling me to have the motor disconnected from the wheel without constantly pulling in the clutch, ie making it a normal bicycle again, until I pull over loosen the screw, letting the lever out and returning to motor-power.
Surprisingly, it doesn't increase weight that much- my old, all-steel bike went from 20lbs to about 32lbs- and the rolling resistance provided by the extra chain when pedaling isn't bad enough to make me change down a gear from my normal training pace.
I'll take some pics soon and update my MTB's thread.
And no, I am not forgoing bicycling- I love pedal power too, and it rides enough like a normal bike for me to continue training and riding it (as a pedal-bike) frequently. The motor will be used if (A) I am wounded or injured in some way, (B) I am dangerously fatigued, (C) The apocalypse happens and I need to save pedaling strength for place where there's no fuel, and (D) Joyrides outside of the training schedule.