In the similar spirit as go karts, minibikes take motorized two-wheeling down to its most basic form. Old school minibikes are not much more than a frame, two wheels, and a motor!
Six Reasons To Start A Minibike Project
* Inexpensive to buy
* Take up very little room
* Easy to work on
* Very few specialty tools needed
* Can be picked up and transported easily
* Vintage ones are increasing in value
Having such a mini motorcycle is not difficult for you
Rather than replace the old rusty chain, I soaked it in motor oil for about a week then scrubbed it with a brush. It was a little messy, but it saved me the cost of a new chain.
Before trying to remove the old mini-bike clutch, I sprayed the shaft with WD-40 and let it soak awhile. There is a small set-screw comes out from the old clutch hub with an Allen key.
I removed the clutch unit from the sprocket with a three-jaw puller. Before installing the new clutch, I scuffed the shaft lightly with fine Emory cloth, then applied a dot of anti-seize.
replace minibike clutch
I’m presently running a 10-tooth clutch with a 72-tooth rear sprocket. With this gear ratio there’s decent power coming off idle with a top speed of about 20-25 mph.
A torque converter is a simple automatic transmission that has a low and high gear. They are more commonly found on go karts.
Because of the Tecumseh to Briggs engine swap, the throttle cable had been previously rigged to work. The exact method to attach a cable to an engine depends on the engine type and style. I fabricated a new linkage with some 1/8″ welding rod, which allowed a better way to run the throttle cable. Lubricate the cable as needed and keep it out of the rain.
When purchased, this minibike had a frame-mounted on/off switch. I replaced it with a momentary-off button on the right handlebar. (On magneto-powered small engines, the ignition is always on).
Minibike Rear Brake
Band-brakes are commonly fitted to torque converters, but this old mini had one on the rear wheel. A new cable was needed to make it operable again, so I salvaged one from an old bicycle. The procedure was straightforward; I cut off the end of old frayed cable with a Dremel tool, then trimmed the outer casing down to the needed length.
Band brake on old school minibike
TIP: Before installing cable, lubricate the inner cable lightly with oil.
After I got the minibike running and stopping, I noticed a vibration at top speed. It seems to be coming from the front knobby tire, which I will be replacing with a sawtooth-tread tire.
I see ads for cheap minibike projects all the time. The fact that they don’t run should not prevent you from buying them. All you’re really after is the frame and the wheels. Everything else is easy to replace, especially the engine.