Sprockets Gears for max speed

Discussion in 'Transmission / Drivetrain' started by Rconce01, Apr 27, 2012.

  1. Rconce01

    Rconce01 New Member

    Just curious what gearing setup you guys are using on the "80cc" I am running a 36t and I am getting max 41mph on a 28" road bike. Just wondering if going lower or higher on the gearing can get me some more speed. The engine was ported, the head was shaved down, has the billet intake and a tunedpipe exhaust.

  2. HeadSmess

    HeadSmess Well-Known Member

    who ported it, whats the pipe tuned to make max power at, how much do you weigh, and what will you spend?

    theres not much to choose froom between 28t to 36t that isnt a custom made affair... :(

    i got lucky and had a 33 tooth laser cut blank...work stock"take" ;) on 20" wheels mind you...

    36 seems to be the limit....

    slow down and enjoy the ride a bit more! :)
  3. Fabian

    Fabian Well-Known Member

    I hope you have a satisfactory set of brakes to safely stop the bike at 41 miles an hour, should a panic stop be required.
  4. Rconce01

    Rconce01 New Member

    I ported it myself based on the instructions on this site. I weigh about 160lbs and the pipe is off a moped I found in the junkyard. I welded it onto my stock exhaust pipe. It gives it killer acceleration but didn't affect my top speed much. I did have to richen the mix to get it to run 40. On the stock exhaust I could run it leaner. If I need to stop at 40 jumping onto the grass would be the quickest solution. The brakes are regular rubber pads on a dual brake lever. I really thought guys here run faster than 40mph.
  5. motorpsycho

    motorpsycho Active Member

    A bigger rear sprocket will give you more speed, and a bigger rear sprocket will give you more low end torque.
    but, when you gain top end speed with a smaller sprocket, you lose low end torque.
    when you gain low end torque with a bigger sprocket, you lose top end speed.
    wheel and tire size can also change your low end or top speed.
    since you're running 28" wheels, I assume that the tire is about 29" tall?
    you can't get much taller than that for a bike tire.
    if you put a 26" rim in it, you;d lose a tiny bit of top end speed with your 36 tooth gear.
    I think if you wanted to go smaller than a 36 tooth, you'd have to have a custom made sprocket, or modify a small front pedal sprocket to work,
    I have a bmx bike with a 28 tooth front sprocket, so they are out there...getting one to work is another story.
  6. relaxxx

    relaxxx Member

    I have a custom 32 tooth rear I got from a bike shop and grinded down the width. I'm about 240lbs and I get around 36mph top speed. Before I had a 36 tooth and top speed was pretty much the same but the motor was at higher RPM and would cut out after 10-20 seconds maxed out. Very dangerous when it pulls back hard at 36mph if it takes you by surprise! I think it was the bowl running dry. With the 32 tooth it does not cut out, same speed with less fuel consumption. Also if I take it easy and just putt along at 20mph I get around 150mpg. I can still take off from a near complete stop. I would never go back to a 36 or 44 tooth. Recently installed a 420 chain because the original one was fetching up. Destroyed my tensioner and rear wheel!
  7. LR Jerry

    LR Jerry Well-Known Member

    Gearboxes and cvt's with shift kits can give you low end torque and high end speed. However many of us here just ride on the public roadways and stay within our local required speed limits. Hope you're able to find the speed you're looking for. Good luck at the race tracks.