Motorized Bicycle

Who wouldn’t want a motorized bicycle? The plan is simple enough; combine bicycle and small engine in a functional hopefully stylish way that does not end with mutilation or death.  Easier said than done, I must admit.

The bicycle was from my buddy Jacob.  He didn’t have much need for a broken down cruiser and that’s exactly what I needed.  Anyway, when he is ready for it back, it’s his once again.  There are not any major modifications to the bike (yet) and this happens to be a slow moving poject.  The engine is somewhat large for this bike. It is a 5 horsepower Briggs and Stratton 4-stroker that I stripped from an edger.  I have seen this same engine power small go-karts, so I know it has the power.  Figuring out how to get them to work together is all there is to it.

I started by figuring the gear ratio needed to achieve my top speed; in this case I think I figured it to be about 15 mph.  There are countless calculators online to help with this step.  To achieve this, I needed four gears total; one at the engine, one at the tire and two between.  This setup reqires a jack-shaft and a place to mount it. I found both and the engine mount to boot in this nifty little number.

How to mount the engine/gearbox to the bicycle is really what has this project stalled.  I know where I want the engine mounted and as you can see by the photo, I have tried the easiest an most obvious option.  I have mentally explored a dozen other ideas for this aspect of the build.  Most of them include welding or otherwise permanently attaching a more study frame to the bike frame.  I am not against this and I have concluded that it is the only way forward. With some practice and a blessing from Jacob, I will fashon a sturdy frame on which to mount this beast.  Until I get a access to a welder, this project may live in purgatory.  I may need to start a new section of my project book if I aquire a welder of my very own.

A few details to iron out after the engine is one with the bike frame are a solid set of breaks and the throttle cable.  The bike has a coaster break; however, I will be installing a good set of clamp breaks on each tire.  Otherwise I love the rust look or as I call it patina and would not change it.