Setting up a jack shaft

Discussion in 'Transmission / Drivetrain' started by Whiyefox, May 8, 2015.

  1. Whiyefox

    Whiyefox New Member

    So I want to put a chainsaw on my bike and I think I have the mounting figured out but I have some questions.

    I think I'm going with a rack mounting because it seems the easiest and then I'll weld a sprocket to my engine and run a chain towards the middle of the bike where a jackshaft will switch over the the left side of the bike and run down to the wheel itself.

    My questions are

    1) What size sprockets should I buy? My engine is a Johne Deer J3816, a 38cc chainsaw. I'll need a sprocket for the engine, 2 sprockets for the jackshaft, and 1 for the wheel.

    2) Will the welds hold? I don't know much about welding so I don't know if any of this would hold (someone else is doing the welding)

    3) Whats the easiest way to make a jackshaft?

    I can add pics if anyone asks, please help! Any advice is welcome, thank you! :)

  2. LR Jerry

    LR Jerry Well-Known Member

    You can go to Staton Inc. David has a lot of custom stuff you could probably use. Depending on your size and how steep the hills are will determine what kind of reduction you'll need.

    I use a shift kit on my bike and have a 33cc 1.6 HP @7000 rpm 1.2 ft/lbs of torque @5000 rpm, max rpm 8000 engine. The reduction range is 49.21-18.82:1. This gives me 59 ft/lbs of climbing torque in first gear. This means I can go up nearly any hill on the 26 inch tires around 8 mph. The level ground speed is 29 mph. The maximum down hill assist is 33 mph. I'm 250 lbs and my bike weigh 100 lbs. Many of the hills here are over a 20% grade.
    Last edited: May 9, 2015
  3. LR Jerry

    LR Jerry Well-Known Member

    For what you're wanting to do I'd suggest 10-40 on the right side then 10-50 on the left. That'll give you a 20:1 reduction. Use a 410 chain.