Best rear sprocket size

Discussion in 'Hubs, Gearboxes, Sprockets and Chains' started by clay830, Jan 30, 2017.

  1. clay830

    clay830 Member

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    I have a 44t rear sprocket and want to lower it to get more speed to compete with my 45+ mph mini bike. I know I most likely won't get 45mph but just want more speed. What would be the best sprocket size? 36t 34t 32t or 28t? or anything else?
     
  2. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    You're gonna have to give us a lot more info than that to get a reliable answer!!!
    You need to tell us what motor you have (& mods done to it), wheel size, how much you weigh (& more).. :(

    Posting pictures of your bike will also help a lot!
     
  3. clay830

    clay830 Member

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    I just have one of those 66cc 110$ eBay kits. I rejeted the carb. I have 26 inch wheels and Weigh 140lbs. I will also be mostly riding on flat road
     
  4. MotorBicycleRacing

    MotorBicycleRacing Active Member

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    I wouldn't recommend going smaller than a 36 toother.
     
  5. clay830

    clay830 Member

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    why not anything lower
     
  6. clay830

    clay830 Member

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    I was thinking 32
     
  7. crassius

    crassius Well-Known Member

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    the two rules are:

    1 don't get in a hurry
    2 don't get lazy

    try the 36 and if it feels like the motor wil take more, try the 32
     
  8. MotorBicycleRacing

    MotorBicycleRacing Active Member

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    Your motor is stock so I doubt that you have the power or the rpm's

    Figure out your gearing and speed.

    The Chinese bicycle engine has internal gearing of 4.1 to 1 because
    20 tooth gear
    82 tooth gear on the clutch side.

    http://jimsitton.net/ratiocalc/

    Just right click on the file gearratio.exe and select "save link as" and put it somewhere you can find it again. Once it's saved, double click on the gearratio.exe file and it will run.

    The program allows for up to three ratios in series. If you have fewer just leave the unused ratios set to 1:1.

    The program will also calculate speed based on engine RPM, drive ratio,and wheel diameter.
    Be sure to measure the outside diameter of your wheel for accurate results.
     
  9. Chaz

    Chaz Active Member

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    Just a safety check here, before you try to go faster make sure your bike can handle it. Brakes, frame, wheels, tires, etc.
     
  10. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I concur with MotorBicycleRacing... Don't go any smaller than a 36t. (your engine isn't powerful enough for anything smaller)

    I also concur with Chaz on all his points! ;)
     
  11. clay830

    clay830 Member

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    what mods could get my engine more powerful
     
  12. clay830

    clay830 Member

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    where could I find a 34t
     
  13. crassius

    crassius Well-Known Member

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    put "80cc sprocket" into google & read a lot
     
  14. TheNecromancer13

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    Big expansion chamber pipe, port the engine, better air filter, sand down the head for better compression, etc.
     
  15. clay830

    clay830 Member

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    you don't think I've done that
     
  16. clay830

    clay830 Member

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    what would be a better carb
     
  17. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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  18. clay830

    clay830 Member

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    tanks dogg just gonna get me's a little getting used to
     
  19. Nashville Kat

    Nashville Kat Active Member

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    I have used a 34 alloy sprocket I got from Kings Sprockets a few years back- with a stock 66 except for a billet intake, for several years- I'm heavier than you and this bike by its analogue speedo can get near 35, which I've never opened it up to, but it will cruise at 30.

    Of course it's got 700C wheels- actually a back 700 c and still the front 27" inch here. I've had several spokes break on rear 27" inch wheels, but the slightly shorter spokes in 700C seem to make all the difference. The hub is a smooth sided high flanged flip flop hub, drilled then to match the inner disk brake drillings on the sprocket and attached with titanium bolts considerably smaller than rag bolts- s it's a very light affair.

    The best part running a smaller sprocket is that the motor revs and vibrates considerably less at the same speeds. Another advantage is that as the sprocket gets smaller, there is generally more clearance for the chain in the rear stays, so it's easier to get rid of the tensionsr and match the chains with half links if you need to or a rear pedal derailleur.

    If you ran 1.5 or 1.75 tires on 26 alloy rims, and unless you are in very hilly land, you could probably run a 34 or even 32 sprocket and get near the same speed I mentioned. The narrow tires help to pedal start the bike as well and a 415 Industrial trike chain with the same pitch but shorter plates is about half the weight of a 415 kit chain and really lessens chain drain too. You can really feel the difference peddling, so I'm sure the small motor does too.

    Other things you can do is get a jug with a wider intake and a wider billet to match and then run a dellotto or CNS style carb, which aren't pricey these days, but never tried then here- just the NT speed carb. You might even be able to run a 28 with a larger intake and carb. You can also easily put a 700 or 27" narrow front wheel on the front- you have to change or adjust the brake- like you see on a chopper motorcycle, and youll notice a much better roll.

    I also have a cruiser frame with 700 wheels- 28 or 32 mm wide tires and a 50 cc China girl with a 39 alloy sprock bolted to the hub- it will cruise in the high 20's but I don't push it much- just enjoy the quiet smooth ride- I've thought bout going to a 36 on that which might lag in a string wind, but I live in flat Florida.
    xct2
     

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    #19 Nashville Kat, Feb 2, 2017
    Last edited: Feb 2, 2017
  20. clay830

    clay830 Member

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    I have 1.25 tires front and back maybe 1.50 but I think 1.25 they are extremely narrow
     
    #20 clay830, Feb 2, 2017
    Last edited: Feb 2, 2017

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