Attempting first build, have a few questions

S

spartan2553

New Member
I'm looking to put together a chain drive bike using a speed bike with 27 in. tires. The engine I'll be using is a ryobi 31cc weed wacker engine. I'm looking to achieve speeds around 30mph. I was wondering what kind of gear ratio i should use and also where a good place to get the gears and chain from. Any other tips would also be appreciated. Thanks.
 
Sounds like a fun build. If you do the math your self, first you need to know the RPM and reduce accordingly.

Lets say your engine maxes out at 9000, I have no idea but have read 9K. Going from a 3" clutch to 5" pulley. The 3" X 5" again. Then a 9 tooth sprocket to the sprocket on the wheel, lets say 56T. Would give you a ratio of 17.28:1 and a speed of 41 MPH. I used a calculator to do the numbers. Great program. If you switch both 5" to 6, ya get 29 MPH. When ya find that program, play around with it. Most folks suggest 18 to one. Looking forward to seeing what ya build.

Joe, where is the gear ratio calculator posted? I can't find it.

But am sure some one who knows your engine will help out or have a better idea
 
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