Gear Ratio with Predator 212cc and jackshaft

Discussion in 'Hubs, Gearboxes, Sprockets and Chains' started by Predator303, Oct 16, 2012.

  1. JonnyR

    JonnyR New Member

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    why would you leave the governor its easy to take off or out
     
  2. potbunny

    potbunny New Member

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    well im on a budget and couldnt modify the frame...i guess i could take it oput but i still am so confused on gear ratios. whats the fastest speed and ration i could use if i removed the governor? would i be able to ditch the jackshaft? cust i would only use a bolt-on-the-engine kind and i cant find one for the 212cc
     
  3. JonnyR

    JonnyR New Member

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    the AGK bolts on to all the predators
    if you dont have a good budget i would think twice about a 212cc build or at least take your time with it because you are going to have to make/modify a lot of parts if you want to do this if you dont know what you are doing real well you will hurt yourself with this engine
     
  4. potbunny

    potbunny New Member

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    ok illl think about it but i will be with my uncle who can help me with the frame and stuff. i will remove the governor, what ratio will i use not to get the best speed and take off from a dead start?
     
  5. JonnyR

    JonnyR New Member

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  6. potbunny

    potbunny New Member

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    oh ok thanks for all the help...one more question, how do i know the idle and max rpms without a goverbor?
     
  7. JonnyR

    JonnyR New Member

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    idle is always around 2200 and max is 5500 rpm with stock internals you need a tachometer
     
  8. potbunny

    potbunny New Member

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    oh ok thanks so much youve really cleared things up in my head
     
  9. kksbunny

    kksbunny New Member

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    Hey, excuse me, so i recently removed my governor, and i was wondering if i just do about 5000 rpm without upgrading any other part like freewheel, piston rod...... Is it ok to do that? please respond!!!
     
  10. Austritch

    Austritch New Member

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    Hey! Just checking in with my 150cc GY6 fat bike build. I am beginning the final stages with doing my gearing. So far I have (on paper) a 5:1 (12 on the clutch and 60 on the axle) gear ratio on a 26 inch drive wheel. I intend to mount the rear sprocket to where the rear disc brake rotor is now to avoid pressure on the spokes. I will still have and use the front disc brake. What do you think about this ratio? Will it eat up my centrifugal clutch? I think the max rev is about 7000. Questions? Comments? Concerns?
     
  11. Slogger

    Slogger Member

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    Here's a link to a page with a 2 item list- click on Gear ratio exe and it will download a good little program you can use to calculate ratios, plug in different sized sprockets and wheel diameters, add a jackshaft ratio, whatever, and tell your resulting speed vs rpm.
    Good stuff!
    http://jimsitton.net/ratiocalc/
     
  12. Austritch

    Austritch New Member

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    Thanks for the calculator. But I am still not finding answers to my question as to whether the 5:1 (12 tooth drive & 60 tooth driven) ratio would cook my centrifugal clutch or not if I'm running a 150cc motor (red line 7000rpm) which has much more torque than a 49cc. Or should I go for a larger driven sprocket? (80 or 100 tooth)? I am using 26inch fat bike wheels (giant).
     
  13. Agreen

    Agreen Member

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    It's not so much the torque of the engine. I have a Honda 196 that I run with a TAV-2 transmission and a 50t sprocket. That's an overall starting ratio of 1:13.4. Yes, geared higher than tiny engines, but still reasonable for smooth takeoff. I would say that a 1:5 ratio would probably cook the clutch quickly. It's like being able to take off in third gear. Yeah, it's possible. Yes, you can get a higher top speed in 3rd, but you risk burning out the clutch if you use it to start. Doesn't matter if you drive a Viper or a Civic.
     
    #33 Agreen, Oct 23, 2016
    Last edited: Oct 23, 2016
  14. Tony01

    Tony01 Member

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    You wanna run at least a 6.5, better to run a 7.5 or 8. As a single speed I have run a 7 with the black spring in the max torque clutch, but the engine didn't rev out past 4800. If you want good takeoff and top speed run a black mt spring with mixed heavy/regular shoes and an 8:1 or 7.5:1.

    With a stock clutch spring and 5 or 6 ratio the thing won't even move, the clutch will chatter and cook at under 30mph.
     
  15. Austritch

    Austritch New Member

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    Thanks AGreen & Tony01! Exactly the answers I'm looking for! I'm gonna aim at a 8:1 ratio and hope it doesn't cook my clutch!
     
  16. Tony01

    Tony01 Member

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    It'll cook a stock clutch, with the heavier spring it won't cook it, also if your primary ratio is between 1.3 and 1.5 you could use a stock clutch on the jackshaft (outputs to rear wheel)
     

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