Pocket bike powered bicycle

Discussion in 'Motorized Rat Rods' started by NLbike, Sep 8, 2016.

  1. 5-7HEAVEN

    5-7HEAVEN Active Member

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    I took a good look at your video again. The sprocket on the left-side jackshaft is too small to be 30t. If you change it to twice the size of your engine sprocket, your bike will fly! Same with the sprocket on your rear wheel. If it really is 60t, your performance should match or exceed that of the minibike that the engine came out of.xct2
     
  2. NLbike

    NLbike New Member

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    I'll have to look at it again when I get home.. Stuck in the great white north now for 5 weeks! I have the bike in parts now, hoping I could get the time to give it a proper paint job.. The engine is a 49cc pocket bike engine with maybe 2hp? It only has a simple centrifugal clutch.. No gears.. The sprockets are a 6tooth-60 tooth to a 15t- 30(or 27?)t.. The tires are only 20inch.. There are kits that would improve hp to around 4-5, and increase rpms quite a bit.. Even if I was running an expansion chamber exhaust,that would improve my top rpms.
     
    #62 NLbike, Feb 7, 2017
    Last edited: Feb 7, 2017
  3. 16v4nrbrgr

    16v4nrbrgr New Member

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    30:1 to 20:1 gearing on a pocketbike engine from crankshaft:wheel woks good for about 30 to 40 mph respectively on 20 inch wheels. They really liven up when you can utilize the high revs with the centrifugal clutch fully engaged. You can lighten the clutch arms and get more pickup, but it makes it difficult to cruise because it will engage at high rpm only. They are incredibly fun engines, with lots of mod potential!
     
  4. 5-7HEAVEN

    5-7HEAVEN Active Member

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    Sorry I mistook your bike for someone else's one on YouTube. Nice bike man. I'd like to make one like yours, but with shift kit and pedals. Your gear ratio is10.8-12:1. You need 18-20:1 gearing. Simply replace the wheel sprocket gives you 18:1. Your bike will fly. A larger sprocket would give more low end power. Good luck.
     
  5. 5-7HEAVEN

    5-7HEAVEN Active Member

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    Change your engine sprocket from 6t to 5t. Gearing increases to 21.6 to 24:1. More low end power.
     
  6. 5-7HEAVEN

    5-7HEAVEN Active Member

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    My mistake. With 20" tires, your effective gear ratio is already 18:1!

    At 45kph(28.125mph), your engine is spinning 8500rpm.

    You're in the ballpark.:)
     
  7. NLbike

    NLbike New Member

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    Thanks for calculating that! I know some of the more high performance pocket bike engines rpm are closer to 11,000 so that might be a possible upgrade later! (if the price is right!)
     
  8. 5-7HEAVEN

    5-7HEAVEN Active Member

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    Your bike brings back memories.

    A friend of mine started with a Honda 35 engine with Staton chain drive. It went ok, maybe 30+mph. I sold him a used 460 engine, which got his bike up to 53mph on flat ground. He must've been cranking 13,000rpm!xct2
     
  9. Ludwig II

    Ludwig II Active Member

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    Have there been any developments in the far flung frofen norf?
     
  10. Ludwig II

    Ludwig II Active Member

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    Hello? Anyone there?
     
  11. NLbike

    NLbike New Member

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    Sorry! No developments lately! I've had quite a bit going on and the bike has been put on the back burner for a while! Hopefully I can get back to it once the weather warms up a bit.. Still a foot of snow on the ground here in NL!
     
  12. Ludwig II

    Ludwig II Active Member

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    In Britain global warming has meant that snow has been almost non existent across most of the country.
     

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