Centrifugal Clutch chain Drive

[K..R..H]

The acctual tire diameter is 15 inches.

 

[Doc Sprocket]

Okay, good start. Now we need an idea how big/heavy your kart is, and whether you're riding on asphalt, dirt trails, hills, etc. Also, speed and acceleration are a trade-off- which is more important to you?

 

[K..R..H]

ooops no the back is 40 tooth and and the front is 14

 

[anderkart]

Right now your geared to hit around 57mph at 3600rpm. I can understand why your clutches burned up.
With your 15" tires you'd be much better off using somewhere around an 80 tooth axle sprocket.

What brand/model 1" clutch have you been running?

 

[K..R..H]

Ok so my kart ways about 150lbs and i need it for dirt so what size gear do i need

 

[Doc Sprocket]

Since your clutch is shot, when you buy another one, this time get one with a lower tooth count, 10 if you can. This will make reducing the ratio easier.
I really think you need to be in the 6:1 area. 10T and 60T or 12T and 72T, or 14T and 84T. Depending on chain pitch, that may be impossible.
Honestly, a CVT is your best bet if you can swing it.

 

[anderkart]

But if you buy another centrifugal clutch, just make sure its rated for up to 13hp or preferably larger engines.

 

[K..R..H]

yah i did get a nother one and its 13 and runs on 13hp. So what size of gear do i need in the back?

 

[anderkart]

yah i did get a nother one and its 13 and runs on 13hp. So what size of gear do i need in the back?

I'm assuming your running #35 sprockets here.

I'd get one somewhere around 80 tooth for good all-around performance. Your top speed would end up somewhere around 26mph at 3600rpm.

If you were planning on doing a lot of low-speed, stop and go or steep hill climbing, I'd consider a 95 tooth where your top speed would be reduced to around 22mph.

If your riding will be mostly all on all large flat open spaces with hard packed dirt, you could consider a 70 tooth where your top speed would be around 30mph @3600.

With no transmission, it all comes down to compromising top speed for better acceleration, but just keep in mind that gearing for higher top speeds will put more strain on your clutch...

One problem you may encounter with some of these larger sized axle sprockets is that its much easier for the chain to be thrown off than when using smaller ones. For this reason its usually best to use a jackshaft to achieve a final drive ratio for good hill climbing ability and improved acceleration.

If you wanted more top speed ability with any of these gear ratios you could remove your engines Governor and expect it to wind out to somewhere in the 4000 to 5000rpm range.

 

[K..R..H]

whats a jackshaft and i need a smaller one because a 70 tooth would be hitting the ground

 

[anderkart]

You said your tires were 15" tall, a 70 tooth would fit just fine.

The #35 and #40 sprocket diameters are listed on these charts:
http://www.azusaeng.com/Sprockets/AzSDno35.pdf
http://www.azusaeng.com/Sprockets/AzSDno40.pdf


Here's a Jackshaft setup:

And a link to a calculator to setup the gearing: http://www.compgoparts.com/TechnicalResources/JackshaftRatioCalculator.asp

 

[K..R..H]

here some pics of my go kart drive

Remember im only 14 and i built this all my self pls dont leave bad comments and tell me how i could put a gear so it wont hit the ground

 

[anderkart]

It looks like your running a #40 size chain and clutch.

A 70 tooth, #40 sprocket would measure just under 11-1/2" in diameter. With the chain It'd be a little larger, but not over 12".

So If your back tires are 15" tall that should leave you around 1-1/2 inches of clearance between the sprocket/chain and the ground.

Your 70 tooth sprocket would be much more likely to contact the ground while riding over bumps, rocks and stuff, but it would work.

But If you installed a jackshaft, you could select its 2 small gears to properly gear your kart and keep on using your old axle sprocket for much more ground clearance.

If you want to buy a jackshaft kit,
you'll find serveral for sale by clicking on this search link here -> http://www.google.com/search?source...1T4GZAZ_enUS369US369&q=jach+shaft+kit+go+kart

And we would help you select the corect (number of teeth) gears to purchace for the jackshaft so your new clutch would last a long time