noob with ratio/jackshaft questions

[Dschroeder]

Ok...so i'm building a chopper out of an old Arctic cat frame. 60tooth rear sprocket, clutch has 12teeth. I'm going to run a jack-shaft so I can keep the engine centered (6.5 clone) what do you suggest for teeth on the 2 jack-shaft sprockets. I'm lost on how to figure that into the ratios

 

[Adrenaline]

how fast did you wanna go? what rear tire do you have in mind.

 

[Dschroeder]

Running a 3.5-10 rear tire. It's mostly a "pit bike" out at the motocross track so doesn't need to be crazy fast but would like it to pull kinda decent too.

would something like this be ok to use, or should I piece a setup together and go with different ratios?
http://OldMiniBikes.com/Adjustable-5-8-Jackshaft-Kit-41-13T-17T-Lock-Collars-Key-Stock-Weld-On.html

never set up a bike this way so not sure how to go about it at all

 

[JamnJM]

Jackshaft Ratio Calculator

Speed Calculator For Go Karts and Mini Bikes

go-kart racing Gear Ratio Calculator

 

[Dschroeder]

Thanks for the links. Depending on how I arrange the jack shaft sprockets I'll end up around 5/6:1. Is that a decent ratio for cruising around and still have decent power/acceleration?

 

[Oldsalt]

For a pit bike I'd want lots of low end. You will be starting and stopping often with no high end ever used. 7 or 8 to 1?

 

[heatley571]

what kind of arctic cat frame are you running? i to am going to jack shaft a rigid whisker frame, and am having problems with width...

 

[cxbra]

D, heres a small lesson in jackshaft ratios... say youre running 12/60 (5:1 ratio). If you put a jackshaft on that has say 10 teeth on the input and 10 teeth on the output is is EXACTLY the same as running a 12/60 ratio since they cancel each other out. Same with if you had a 12/60 ratio and added a 20t on the jackshaft input and a 20t on the output it would be the same 5:1 ratio. Now when your jackshaft sprockets are different teeth sizes then you'll have to do some calculating. My tip doesnt help much, but it really helped me out in understanding ratios.