Need help with gears on chainsaw bike

Sidewinder Jerry

Well-Known Member
Dec 19, 2011
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Rockwood, TN
With China girl engines they which are actually 66cc they generally run a total reduction between 11:1 to 14:1. The engines that run a reduction under 5:1 are the 212cc.

As for gear ratios a 9t is around the smallest you'll find that'd be practical to use. I recommend this engine to jack shaft 10:40; jack shaft to rear wheel 10:40 for a total reduction of 16:1.

Here's your speed formula:

RPM÷(1056× total reduction)×wheel diameter × ⚻

6000÷(1056×16)×27.5×⚻=30.7 mph.

That's a very realistic build for a first time DIY build. I also suggest for the small sprockets to use 410. This way you can use 410 chains.
 

Mrgoodcat

New Member
Jul 25, 2021
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Ok wat would u suggest for gearing for a result of 45mph im looking for something to go fairly long distances so I need to have it go a little bit faster
 

Sidewinder Jerry

Well-Known Member
Dec 19, 2011
1,468
306
83
59
Rockwood, TN
Ok wat would u suggest for gearing for a result of 45mph im looking for something to go fairly long distances so I need to have it go a little bit faster
Your engine is too small to realistically expect to do 45 mph. At best you might could get up to 35 mph provided you aren't a very large person and you don't have any really steep hills to contend with.
 
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Mrgoodcat

New Member
Jul 25, 2021
21
4
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iv got everything set up right,,, i think ,, and it wont start ? i checked the wiring, plug and fuel everything seems to be in order ,, wats up?