need the right sprocket set up... help!

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dirtracin

New Member
May 21, 2012
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cincinnati
Im in the process of building my first chopper and I have come across a gearing issue I just cant seem to figure out... so Im building a bike with a 110cc engine w/auto transmission going to a single speed wheel and between the two is a jackshaft... the engine came with a 13t sprocket but can get any size between 11t and 15t... from there to the jackshaft due to space I only have room for a 9t to 13t... now from the jackshaft to the wheel, I can use between 9t to 15t.. from there to the wheel which has a 21t...

What would be my best options?....
Im open to any and all sugestions.... thanks for the help
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
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Ridin' inSane Diego, CA.
Welcome to the forum (^) It all depends on what you want the overall gear ratio to be. What max speed are you looking for? How hilly of a area are you going to be riding in? There are many varibles based on the application.....you've got good power to work with a 110cc.

With the gearing parameters you have there, the lowest gearing I could work out is 2.69:1......which is way too tall for all intents and puposes.

You are going to have too decrease the sprocket on the engine and/or dramatically increase the rear sprocket on the back wheel to get things to work properly.



dnut
 
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dirtracin

New Member
May 21, 2012
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cincinnati
thanks for the response scotto... I knew Id get some answers here!..overall top speed 45mph + would be nice if possible...I definatley dont want a torque monster....I did forget to mention that I was using a 20 rear wheel and its completely flat where Im using this... if possible Id like to keep the sprocket thats on the jackshaft going to the wheel as small as I can... it would jus look better... can you get me close?
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
dirtracin said:
thanks for the response scotto... I knew Id get some answers here!..overall top speed 45mph + would be nice if possible...I definatley dont want a torque monster....I did forget to mention that I was using a 20 rear wheel and its completely flat where Im using this... if possible Id like to keep the sprocket thats on the jackshaft going to the wheel as small as I can... it would jus look better... can you get me close?
Click to expand...
Yes, all that info helps alot, gemme a couple mins and I'll see what I come up with.......it sounds like the rear wheel sprocket is on the right side, correct?

11t to 13t then 9t to 40t (if you can run a 40t on rear) will yield 5.25:1 ratio and at 5,000rpm with a 20" rear wheel 56.6mph.

That is still really tall gearing. If you can run a larger than 40t sprocket on the rear, this would help alot.

If you can run a 50t on the rear, the same gearing will get you 6.57:1 with a speed of 45.3mph at 5,000rpm.

hope this helps...
 
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dirtracin

New Member
May 21, 2012
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cincinnati
wow what precision....very nice... I really wasnt expecting that kind of info.... Yes my sprocket is on the right side.... and where do I find the 40 and 50t sprockets? also Im using a 4"stingray rear wheel if that helps...
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
OK, then again I am assuming his is a coaster brake rear hub that uses a single cog (Shimano cb110 type ) with the 3 tabs and snap ring. I'm not sure where to get a spocket of this size for this app (I'd tell you if I knew) but I'm sure one could be adapted if nothing is readily available. Hopefully someone will chime in with some insight on this matter. Hang in there dirtracin...
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
dirtracin said:
its a freewheel
Click to expand...
Well then, you might be able to use a freewheel like those on the Grubee HD hub and axle if the threads are compatable. If the threads are compatable but the freewheel works in the opposite direction it should, you could braze (or have it brazed) solid. With that you could run the 5 -bolt mount, large center hole 44t, 50t and a few other sprockets just fine.
 
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pbeggs

New Member
May 6, 2012
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maine
replace the freewheel with a sick bike parts crankset freewheel then bolt on a 48 tooth sproket (or any other one )
 
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dirtracin

New Member
May 21, 2012
5
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0
cincinnati
ok guys thanks for all the help... I found a rear sprocket kit with a 50t my next question is what size chain will this use.... the only thing I found said 415, but I cant find any 415 countershaft sprockets for a 5/8 axle...
 
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