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Hubs, Gearboxes, Sprockets and Chains Can't find 'em, grind em - hubs and transmissions, problems and modifications to make you run smooth and trouble free

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  #31  
Old 10-15-2016, 11:46 AM
Slogger Slogger is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

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/
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  #32  
Old 10-23-2016, 04:58 PM
Austritch Austritch is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

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).
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  #33  
Old 10-23-2016, 08:48 PM
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Agreen Agreen is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

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.
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Last edited by Agreen; 10-23-2016 at 09:20 PM.
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  #34  
Old 10-24-2016, 01:41 AM
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Tony01 Tony01 is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

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.
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  #35  
Old 11-01-2016, 09:53 PM
Austritch Austritch is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

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!
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  #36  
Old 11-11-2016, 08:36 PM
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Tony01 Tony01 is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

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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