Chains Pocket bike engine from sprocket to sprocket with chain

Discussion in 'Transmission / Drivetrain' started by Stephencatfish, May 6, 2012.

  1. Stephencatfish

    Stephencatfish New Member

    Is it really that easy with added kill switch and throttle and of course... Mounting the motor??

  2. Al.Fisherman

    Al.Fisherman Active Member

    What are you really asking? Mounting a engine in a bike frame is a piece of me it is.
  3. Stephencatfish

    Stephencatfish New Member

    If I buy a pocket rocket little 33cc or 49cc and to install it is to mount the engine then take a chain and connect sprocket to sprocket with a kill switch and throttle and maybe a chain guard?? Is it really that simple or am I missing something ??
  4. lowracer

    lowracer Member

    You will need a jackshaft or transmission to get the correct gear ratio to run the rear sprocket. My PB engine turns max 11K rpm so I use ~15.6:1 ratio for driveable speeds (I am running a 1.5" vbelt pulley to a 22.5" rim pulley). Using a PB clutch w/ 6T would require ~95 teeth rear sprocket if no jackshaft or tranny...
  5. Stephencatfish

    Stephencatfish New Member

    So I can use the pocket
    Bikes clutch sprocket so if it has 6 teeth I need a rear sprocket to have 95 teeth??

    Can u pm me your email ty
  6. lowracer

    lowracer Member

    I dont think there is a sprocket that large available, & if there were you wouldnt want such a large heavy flywheel on your rear wheel. You need to look into building a jackshaft or purchasing a gear reduction transmission (check out There are some handy gear ratio calculators on this site to measure & get the correct ratio. I dont run chain drive (just vbelt) but there are others on this forum that you can 'search' & find threads related to what you are trying to accomplish.
  7. HeadSmess

    HeadSmess Well-Known Member

    with single reduction, you need a sprocket almost as big as the wheel you are driving.

    so, saying "95" teeth is irrelevant, as the ratio required is governed by wheel diameter.

    the engine will turn at so many rpm. at a given speed, a large wheel will complete less rpm than a small wheel. the reduction needs to be calculated by wheel size.

    invariably 16:1 on a 26" wheel. 12:1 on a 20" etc...depends on engine, terrain, weight....

    and those 6 tooth pinions onthe rockets are cruel to chains! they love to throw them! chew them! snap them! wear them out!

    they do work, mind you, but theres the dirt bike versions that have a small reduction already fitted, and run a larger output sprocket... much nicer.

    it takes roughly 5 attempts to make a GOOD motorised bike from scratch. after that, theyre invariably perfect until you try getting fancy again...