Suggestions for my first motorized bike?

Discussion in 'General Questions' started by codi79, Mar 21, 2008.

  1. codi79

    codi79 Member

    I have a Poulan Weed Eater 20cc motor. I know its not big but I just want to be able to build a motorized bike. I am not sure wether or not to make it a friction drive or chain drive. I am kind of leaning toward chain drive due to slippage in the wet with a friction drive. I also dont know how or where to mount the motor? Over top the rear wheel? In between the frame? Oh, and one last thing, I dont have a welder and I would like to build the whole thing without welding and i would like to be able to disengage the motor so i can return to normal pedaling.


  2. Demosthenese

    Demosthenese Guest

    Mounting an engine not designed for motored biking is fun, but requires much tinkering. If you don't have a welder and are trying to desing things like a quick release engine mount, you're going to very quickly run into a large amount of fabrication work that you cannot do.

    Look through the forums for ideas first man, it sounds like you haven't thought this through all the way.
  3. Welcome.....Definitely a challenging problem.....I would recommend chain drive if at all possible....As you mentioned tires can be eaten quickly with the friction drive....I can attest to that first hand.....Good Luck...Post pics if you can I'm sure we'd love to see your progress!
  4. codi79

    codi79 Member

    Okay, I noticed that I was getting a bit eager with the idea of a disengaging system, so I've decided that Im not going to build a disengagment system.

  5. Alaskavan

    Alaskavan Guest

    Codi, If you frame-mount it, and run chain, you can buy a hub with a freewheel on the left side, so it will ride just like a bike when the engine isn't running (I just had an electrical problem in the middle of a 14 mile ride, it can be handy to be able to easily pedal). As far as mounting, etc. Haggard posted an excellent tutorial. Ignore the fact that he was talking about Pocket Bike engines. Most of the info should be applicable.
  6. codi79

    codi79 Member

    Thanks! Do you think I can run the chain straight from the motor to the rear sprocket of a reqular mountain bike. A least that way I can choose which sprocket on the freewheel. Am I right?

  7. Alaskavan

    Alaskavan Guest

    If you run from the engine to your pedal side rear sprocket, there are a couple of problems you'll have to overcome. 1. Getting the gear ratio right (you need about an 18:1 reduction on a 26" wheel), and 2. The pedals would turn when the motor runs. You need to have the engine drive independent from the pedal drive.