brand new clutch wont pull

[codywayne73]

i did a 18hp twin boxer engine swap on my gokart and since a couple reasons i cant run any lower gear ratio for sprocket and its like a 2.5/1 gear ratio on 9 inch wheels

when i tested it today it barey engages when on stands full rev and barely rolls when bouncing off rev limit

and the clutch is for 13hp not 18 though

is the clutch probably bad or is it entirely the gearing

 

[Whitetrashrocker]

Post some pics of your set up.

 

[Denny]

That gear ratio will never work! 5:1 maybe.

 

[Darren]

I run 17-82 on my go kart, pretty standard. I'm about 22hp using a noram stinger clutch.

Could do with some photos as Whitetrashrocke requested

 

[JimD]

Clutch will not work, you need a torque converter and like Denny indicated you need to get the gear ratio that you have corrected. When you say 9" wheels you are talking the rim size not the diameter of the wheel, correct? The important number is diameter of the tire from the ground to the top of the tire, a clutch will handle 12" but anything larger than that you better get a torque converter. Use a 6:1 ratio and you will get it to move. The ratio you have on it now will move you from the moon to earth if you are going on on the downhill route.

 

[JimD]

Figuring a gear ratio for new people to karting you take the number of teeth on the smaller sprocket either on the clutch or the jackshaft and divide that into the number of teeth on the rear sprocket. A clutch with 12 teeth will normally go to a rear sprocket with 72 teeth 12/72 =6 So we have a 6:1 gear ratio- for every tooth on the clutch there are 6 teeth on the rear sprocket. When you throw in the torque converter you improve the ratio even better, most come with a 6" driven but my preference is the 7" driven. The 6" was more for mini-bikes driving a single wheel while the 7" driven helps because most go karts are live axle which means both wheels on the rear axle turn at the same time. (Stub axle means only one wheel turns so you tend to wear out the drive wheel much quicker.)

So when you use the torque converter 7" driven you have a low speed gear ratio of 3.1 and as the belt drops down into the driven and rises in the driver for the high speed ratio it goes up to a 1.4.

Anytime your rear tire exceed 13" diameter (from the ground to the top of the tire) you should be looking to put on a torque converter.

 

[bob58o]

I believe the 7” Driven from Comet (31D7) is 3.1 : 1 in Low and 1.12 : 1 in high; (maybe knockoffs are different?).

compared to 2.68 : 1 in Low and 0.90 : 1 in high with the 6” Driven Unit.

 

[JimD]

Bob- I stand corrected, your 1.12 is correct in high for the 7", old fingers and not proof reading what I typed.