sprockets and clutch help please

[nawizzel15]

hi i just finished making the frame for my mini bike now i need to attacht the tires and engine but first i need to kno something i dont have a clutch for my engine yet (from edger 3 hp) and i have a sprocket from my bicycle its 45 teeth i want to know if i need specific ratios between the clutchs teeth to the back tires sprocket? and if i do need a specific ratio between the two sprockets wut are the ones to use to get the chopper as fast as possible?

if i didnt word correctly or something please say something so i can be more clear

 

[Russ2251]

Bicycle chain/sprockets aren't really designed for anything beyond human power. Standard minibike chain would be #35 or #41. Also, as far as I know, no manufacturer makes a clutch that utilizes bicycle chain.
Common ratios are anything between 4 and 6:1.
If drive wheel sprocket is 72 teeth (#35 pitch chain) and clutch has 12 teeth, then ratio would be 6:1 or 72 divided by 12 = 6 and would give you great low end torque.
If you went to 60 teeth on drive wheel and 11 teeth on clutch, ratio would be 5.45:1 or 60 divided by 11 = 5.45. You would lose some low end torque but gain some top end speed.
Size of tires also plays a part in all of this.

 

[nawizzel15]

2 more simple guestions please first would it be better to make the chain longer or shorter between the clutch and sprocket to get the most speed out of it? and would my 3 horsepower engine be strong enough to engage a centrifugal clutch?

oo and ps i think im going to go with a 12 to 72 ratio

 

[jr dragster T]

horsepower does not determine how the clutch engages. As long as the engine revs to about 1800-2000 RPM then it can engage a centrifugal clutch.

 

[Russ2251]

Should be the slightest amount of slack in chain. Never tight. There is a spec but don't recall what it is. I'm sure someone else does.
Keep in mind that chain will gain slack over time. Some folks believe that chain stretches but is actually due to worn bushings and associated pins.
As far as hp for clutch engagement goes, I've run .8 hp with no problems. As Mr. Tyler stated, RPM is key.