49cc razor pocket mod gear ratio

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kidgambit

New Member
May 2, 2012
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washington
I'm gonna put a 49cc pocket bike engine I rescued and got running into a razor pocket mod frame. But a guy on YouTube did one and the stock rear sprocket is to big and makes it go slow. It is a 12 inch rim the engine has a 7 tooth sprocket. What tooth rear sprocket do I need to get more speed. Please help laff
 
cannonball2

cannonball2

Well-Known Member
Oct 28, 2010
3,682
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Colonial Coast USA.
You didn't say what the transmissions reduction is. Some are 3:1 some are 5:1. Assuming a 3:1 If you ran a 14 on the trans and a 40 on the rear wheel and the engine makes 8500rpm the top speed is 35mph. You need to know which trans you have.
 
cannonball2

cannonball2

Well-Known Member
Oct 28, 2010
3,682
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63
Colonial Coast USA.
OK I assumed it was a CAG engine. Running what you have @ an rpm of 8500 is good for about 25mph.

I found a 10t on ebay for the front. Its cheap and easy to change. Used with your 80t rear it will get 37mph. This is assuming your engine will pull the ratio and will rev to 8500. That's pretty fast!!
 
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