Gear Raitio ?!?!

[kart mania]

well i dont really know what clutch i should get cause im so confuesed about gear ratio. i have a 54 tooth sproket on my kart (that weighs like 200-250lbs) and the only clutch that i can find that has a 1'' keyed shaft has 10 teeth witch i dont know if that will work or notwill it or will i have to change it?

 

[r97]

what is your tire dia, and where will you be riding, weight of kart with passenger(s), engine hp, engine crank dia?

 

[kart mania]

well my tires are 18's and off road with a lttle bit off hills and with me on it, it would weight around 380lbs and it's powerd by a 9 hp honda (it's not a clone)and the size of the crankshaft is 1'' inch it is keyed and threds at the end

 

[redsox985]

Find a Comet 40 series TC, you could probably get away with a 30 series or GTC copy, or wait a bit for GTC to make the 40 series copies and sell them.

 

[kart mania]

the thing is i wasnt looking on spending that much would i have to change the sproket for it to work out better

 

[redsox985]

You would probably need a larger rear sprocket with a ration near 7-8:1 because most centrifugal clutches are 6:1 and that's for smaller tires than yours. Cent. clutches shouldn't be used on tires much taller that 16" unless the ratio is very low.

 

[r97]

hay all i can say is that the gtc 40 series are coming out soon, and don't cost much more than a 1" bore cent clutch.

 

[kart mania]

well i found out that i can get a 14 or a 17 tooth clutch now does that make it any better?or will they burn up if i try it if that wont work i will just go on ebay and find a cheap tc setup from comet or whAT ever

 

[r97]

nope, not unless you get a bigger rear sprocket, or setup a js. comet will prob be expensive unless your lucky.

 

[kart mania]

if i get the 10 tooth clutch what size of sproket should i get for the axle?

 

[devino246]

if i get the 10 tooth clutch what size of sproket should i get for the axle?

Can you get a 10 tooth clutch with a 1" bore? If your going with 10 teeth on the engine, something along the lines of a 70 tooth sprocket would be recomended. Basically, your gonna need to buy a jackshaft, because a 10 tooth clutch would need to use #40/41 chain and a #40/41 70 tooth sprocket would be HUGE.

 

[kart mania]

that whats already on it, it has 40 style chain with a 54 tooth sproket that takes #40 chain

 

[Doc Sprocket]

Kartmania, I think you're confused...
Devino said you'd need a 70T rear. That's not what you have.

 

[kart mania]

i know i dont have one im saying if i had a 10-70 tooth ratio would it work good enough to drive around off road

 

[Russ2251]

If you are going to use a centrifugal clutch with 18" tires, you are going to need something close to a 100 tooth sprocket.

 

[redsox985]

Or a TC, or 10 on your motor 30-35 on the jackshaft then 10 on the jackshaft and 30-35 on the rear end.

 

[Bluethunder3320]

100 tooth sprocket.

lol, does anyone make them?

 

[Russ2251]

My point is that 5, 6, or 7:1 sprocket ratios are fine for a gokart sized tire (10-11" diameter, more or less), but cannot be applied to an 18" tire.
Very generally speaking, a driven sprocket should approach the tire diameter to within 2" under the tire size.
In other words, an 18" tire would require a 16 inch diameter (approximately) driven sprocket...especially for off-road use.
A #40 100 tooth sprocket translates to 16 inches in diameter.
I run 70 tooth drivens with 17 tooth clutches (#35 chain) with 11" diameter tires and 17hp.
My ratio is 4.12:1. A little steep but gets me up to 50mph in about 300 feet.
I drive on asphalt only.

 

[redsox985]

Well, I think a torque converter or jackshaft setup is the only option. And the jackshaft will produce horrible top speed for when you aren't offroading.

 

[Russ2251]

I think a torque converter or jackshaft setup is the only option.

I whole heartedly agree, especially at 250lbs.