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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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  #1  
Old 10-16-2012, 07:38 PM
Predator303's Avatar
Predator303 Predator303 is offline
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Default Gear Ratio with Predator 212cc and jackshaft

Not quite sure where to post this but maybe someone with experience with this engine can give me a tip before I order the sprockets.

I bought the engine from somebody in this forum and he ran the following setup

13t clutch
22t JS in
9t SJ out
48t rear sprocket

I get a ratio of 9.026



He said he had around 50mph at 6700rpm

Now my goal is a good cruising speed of 50mph at a lower rpm

The website where I can order the jackshaft only offers the JS sprockets from sizes 10 to 18 and it would be great to order everything from one place.

So if I order the clutch with 12t then 18t in, 10t out and to a rear sprocket of 44t (which i still have around here somewhere)

I get a ratio of 6.600



If I calculate right, this would mean I can go same speed (50mph) with about 4904rpm. Which sounds perfect but then again I think it might be a little too long the ratio because of the start from dead stop.

Now from what I heard the engine got lots and lots of torque so here is the question:

Do you think this is a too long ratio for launching from dead stop?

Compared to my current bike with a slightly tuned (higher compression) 80cc running a 34t sprocket in the rear I can still perfectly launch from dead stop without paddling so im pretty sure with a monster like the Predator it should be no problem with this ratio setup. Or not?

The clutch I want to get engages at 2.000rpm

Last edited by Predator303; 10-16-2012 at 07:40 PM.
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  #2  
Old 10-16-2012, 08:38 PM
dmb dmb is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

carefull if thats the one i think it is. it can spin the hub clamp right through the spokes. looks like you got your wish. very good deal. now buy a big shoehorn. dennis
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  #3  
Old 10-16-2012, 09:02 PM
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Predator303 Predator303 is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

Can somebody explain me the different options they sell here and why you would either recommend a jackshaft or torque converter? And also - what rear sprockets are being used in the case of the converter??

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  #4  
Old 10-16-2012, 10:23 PM
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Predator303 Predator303 is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

Nevermind. I ordered everything
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  #5  
Old 11-27-2012, 09:02 PM
potbunny potbunny is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

what did u order and where from? is your engine stock, or is the governor removed? i am also making a bike and want a good speed, did yours turn out ok?
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Old 11-27-2012, 09:15 PM
JonnyR JonnyR is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

take a look at his build thread most of your answers are here and its a sweet bike

he got it already race ready from another member and saved a boat load on it

governor is long gone look for buck0s videos he posted in the thread i linked

what kind of speed do you want is the key to all of this this is a bicycle still
http://motorbicycling.com/showthread...light=predator
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  #7  
Old 11-27-2012, 09:21 PM
potbunny potbunny is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

i dont think i want to remove the governor as ive been told that it reaches 5500 rpm max with it...i was looking at 50 or so its on a chopper with pretty thick tires. i am completly ignorant to gear ratios, clutches, rear sprockets and all of that jazz, i honestly have no idea what im doing at this point. i really just want to run a chain from a 12 tooth clutch that engages at 2800 to a 55 rear sprocket and see what i get...do you think that will work? what are your suggestions?
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Old 11-27-2012, 09:36 PM
JonnyR JonnyR is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

all governors are set to 3600

and you need a 10:1 reduction from the motor since its a chopper you dont need the offset like the rest of us do but it may need to go the other way so you may still need a jack shaft
to work right it would be a 120T rear sprocket a 55t if you could make the power to pull that gear is something like 80-90 MPH the gear reduction is the other reason we use a jack shaft so we can use a 40-55T rear sprocket its taken up at the jack shaft
__________________
Are you callin' me crazy! just cuz i got a hotel in my foot doesn't make me a boogali moogali moogali

Schwinn jaguar with a 66cc flying horse
they all run fantastic till they don't

smoke tires not drugs
YES! YES! JESUS H. TAP-DANCING CHRIST... I HAVE SEEN THE LIGHT!
http://www.youtube.com/watch?v=YoPVC4YxDlI
http://www.youtube.com/watch?v=y0O7_...eature=related
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  #9  
Old 11-27-2012, 09:39 PM
potbunny potbunny is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

so i need a jackshaft? what sizes do i need on the jack shaft and rear sprocket? the same as predator did above? i would hate to take out the governor and i dont want to unless i really have too. what size sprockets should i use to get maximum speed?
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  #10  
Old 11-27-2012, 09:54 PM
JonnyR JonnyR is offline
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Default Re: Gear Ratio with Predator 212cc and jackshaft

it idels at 2200 if your clutch in gauges at 2800 and the govenor is at 3600 that gives you 800RPM to use

the sprockets arnt hard to work out its division mostly if your clutch is 12T and your rear is 55T thats 4.58:1
with the suggested AGK jack shaft ratio 12T clutch 22T in 9T out and a 56T rear is 12.44:1
if you switch to a 44T rear or a 11T on the output of the jackshaft it brings it close to 10:1
__________________
Are you callin' me crazy! just cuz i got a hotel in my foot doesn't make me a boogali moogali moogali

Schwinn jaguar with a 66cc flying horse
they all run fantastic till they don't

smoke tires not drugs
YES! YES! JESUS H. TAP-DANCING CHRIST... I HAVE SEEN THE LIGHT!
http://www.youtube.com/watch?v=YoPVC4YxDlI
http://www.youtube.com/watch?v=y0O7_...eature=related
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