dazed and confused

[getting kart smart]

I just got done with a home made go kart. I went to take it out and it's really slow taking off. Does pretty good after I finally get going. But by the end of the 2 minute ride the clutch was smoking hot. The kart is about 250 lbs. I am 170 lbs. This is my sprocket ratios. I have a 11 tooth clutch on the motor going to a 17 tooth on jackshaft. Other side of the jackshaft I have a 10 tooth going to my axle sprocket which is 42 teeth. 17 inch tire radius. I marked the clutch and the tire and the clutch went around 7.1 times to the tires 1 revolution. So I guess I have a 7.1 : 1 gear ratio. That's what I was trying to target. Is that not a good ratio for offroadin, or do I have a bum clutch?

 

[exenos]

That ratio is way too low with 17" tires. Try something like 10:1 - 15:1

 

[landuse]

Here is how you work out the ratio that you have now:

(JS in/Clutch)*(axle/JS out) = ratio
(17/11)*(42/10)
1.545*4.2 = 6.49:1

So your ratio is 6.49:1. Generally this isn't too bad for a kart, but you have really big tyres (17"). This means that you will have to gear a bit lower. I would maybe suggest 8:1 or maybe 10:1. I wouldn't really go lower than that. Sorry Exenos

When your gear ratio is too high, you burn your clutch really quickly. It is like you are taking off in 3rd gear. You can go pretty fast in that gear, but getting there kills the clutch.

Gearing lower will reduce your speed, but if you are doing offroading it is not going to matter. At 8:1, you will go a theoretical 23MPH.

I would get a sprocket with around 25T for your JS input. This should sort you out

 

[exenos]

I had mistaken this with another thread where the op said that he was in a very hilly area, hence the high ratio. Sorry for the confusion.

Although you don't want anything lower than 9:1 because that is the equivalent of 6:1 in a kart with 13" tires, you might even want to do 10:1 as a minimum because there is a lot of extra tire mass that you have to move.

 

[r_chez_08]

I would aim for 9:1 or higher.
Or get a torque converter.