first build help weed eater

Discussion in 'Transmission / Drivetrain' started by berto31565, Apr 9, 2013.

  1. berto31565

    berto31565 New Member

    hey everyone. my name is Robert. i have been wanting to build a motor bike but all i have is weed eater motors. i dont have the money for a chinese motor so i was wondering how would i be able to start the motor without the wheel spinning. i realize the clutch engages or whatever but when will it actually engage and send power to the wheel? is it possible to have some sort of linkage? or does it work off of rpm?idk thanks for all suggestions or tips

  2. Anton

    Anton Administrator Staff Member

    Are your weed eater engines pull start/ centrifugal clutch? You can pull start it to get it going. To take off give it throttle and the centrifugal clutch will engage when the RPM's are high enough.
  3. berto31565

    berto31565 New Member

    yeah they are pull start. and have the clutch and clutch bell so if i'm understanding correctly the momentum of the crankshaft spinning expands the clutch and then spins everything. do you think that the added weight of the pull from the sprockets make the clutch slip or would it be alright?
  4. wheelbender6

    wheelbender6 Well-Known Member

    Some guys build a lift clutch into their engine mount. it is literally a hinge in the engine mount, allowing you to lift the motor slightly off the tire using a cable or lever. Should be some good examples on this site somewhere. sells a kit that has only a lever operated lift clutch and no centrifugal clutch.
  5. berto31565

    berto31565 New Member

    i would prefer chain driven though
  6. Anton

    Anton Administrator Staff Member

    You can easily pedal to help get it off the line.

    For a chain/sprocket driven weed eater bike you will have to work out some gear reduction. The drive shaft of a weed eater spins at very high RPM's so you need to reduce that down. This is why they make such good friction drive engines with a small diameter drive shaft roller straight onto a large diameter tire. The chinese motors have an internal gear reduction of 4:1. You would need to achieve something similar if you wanted to use the same sized sprockets as the chinese kits.

    To get a desirable ratio you would need to add a jackshaft for gear reduction. Here's some talk about weed eater gear ratios
  7. berto31565

    berto31565 New Member

    thanks i appreciate it. another thing what would i do if i have a motor on a mountain bike with multiple gears, how can i make the chain go to another sprocket while still rotating?
  8. Anton

    Anton Administrator Staff Member

    The sprocket is mounted on the left hand back wheel. Opposite side to the mountain bikes gears. I still think the simplest option for a weed eater engine is a friction drive setup.
  9. Hey, I'm doing a weed eater bike, my motor has a clutch. Is it better to use a motor with a clutch or without?
  10. 5-7HEAVEN

    5-7HEAVEN Active Member

    With a friction drive, without a clutch and with a hinged lever.

    With gears, with a clutch. However, the weedwhacker clutch won't allow you to pull away from a standing stop. You'll have to pedal until the bike's moving along, then throttle the engine.

    Just my opinion.
  11. Steve Best

    Steve Best Well-Known Member

    Hmmm, on limited funds, that is called "champagne tastes on beer wages"!

    It doesn't take long to exceed the cost of a China Girl kit when you start fabricating.