Gear ratio Help w/ chain saw bike!

Discussion in 'Rack Mounted Engines' started by MAXPOWER105, Aug 27, 2010.

  1. MAXPOWER105

    MAXPOWER105 New Member

    I mounted a chainsaw to the back of my mountain bike with a gear ratio of 10:1. the motor is 35 cc and of course has a clutch, learned my lesson. Is this gear ratio going to be ok? i figured i could pedal up to speed then engage the throttle and it wouldnt tear up the clutch.

  2. srdavo

    srdavo Active Member

    what lesson did you learn?

    20:1 will work so much better.

    at 10:1, you'll have to pedal up to about 25mph, before your engine will begin to pull you...and it won't pull you well.
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    10:1 Gear Ratio?

    How are you getting 10:1 ratio?:detective:

    FWIW, the higher the number, the lower the gear ratio. The lower the gear ratio, the less strain on the clutch.
  4. MAXPOWER105

    MAXPOWER105 New Member

    i made an entire mount and everything for a chain drive w/ a weed whacker w/ out a clutch just to realize i couldnt get the dam thing started so i went and got a chainsaw off craigslist. So now I have an engine and no idea what to do with it.

    So what your saying about the gear ratio is that it is still to low, idk how to make it any higher i used the biggest sproket i had for the wheel and the smallest for the clutch, i was really hopeing ten to one would be ok but i dont know anymore
  5. MAXPOWER105

    MAXPOWER105 New Member

    I have a ten to one gear ratio with a 6t on the sproket and a 60t on the wheel of the 26" mt bike, its a chain drive by the way
  6. MAXPOWER105

    MAXPOWER105 New Member

    sproket*= clutch my bad
  7. 5-7HEAVEN

    5-7HEAVEN Guest

    What size chain are you using? 8mm? #25?

    You need to make an intermediate shaft, aka jackshaft. This will connect the engine sprocket to the wheel sprocket by their chains.

    Your 6t engine sprocket chains up to a 24t sprocket on the jackshaft.

    24t/6t = 4:1

    Then a 12t sprocket on the same jackshaft chains up to your 60t wheel sprocket.

    60t/12t = 5:1

    5:1 X 4:1 = 20:1