Originally Posted by johnny smith
ever since my buddy reminded me about using a chainsaw on a bicycle ive been thinking about building a 4 wheel bicycle (square type-ish). what i wanna do is take tires from a 21 speed (or however big they get, as i havent exactly looked at bikes in last 5years so idk bout it) mountain bike and kinda make myself a 4 wheel type bicycle with gears (from the bicycles themself which idk if thats possible). to sum things up, it would be 4 mountain bicycle tires, seating supported by middle mounts and 2 of the biggest chainsaws in the back chained to gears on the rear axle. i have no welding tools or any of the stuff, once i find out what i can do as far a building it ill start getting the stuff i need....i understand what i described might be too much weight and ive considered that and decided i might need bigger than a chainsaw...
pretty sure i left stuff out so if u need any additional info just let me know
A bicycle w/4 wheels is no longer a bicycle.
There are Honda GX200 engines and Chinese copies of them that are now the engine of choice for the beginner's classes of kart racing. Engines typically cost a little over $100, new. They make 6-1/2-7HP, are 4-stroke (so no messing w/mixing oil in the gas, fouling plugs, etc. not to mention that 2-strokes are notoriously peaky, temperamental and running 2 of them instead of one correct engine will likely go slower not faster, will drink almost twice the fuel and will handle and stop worse than a single engine'ed project.
Forget about using the derailleur gears from a 10 speed. The engine I mentioned above can easily use a centrifugal clutch mounted directly to the end of the crank. There are variable ratio belt/chain driven trannys also available for kart and mini bike applications if you need "gears".
Research 4 stroke karts and you'll get a better idea of what's available to easily and cheaply power your deal.