Clutch help

I’m in the process of building my first kart. I’m running a box predator with 10.8lb valve springs and I don’t have a clue on what clutch and why. I don’t understand the difference in 4 springs vs 6 springs, 2 disc vs 1 disc. Price difference seems to be several hundred dollars. I’ve read that optimal rpm is around 4800-5100 in racing trim. any insight would be appreciated.
 

meracer9

Premium User
2 disc, 6 spring Bully or something of that nature is what I'd suggest. Look up JP Curry on here JPM Karting/31 Engagements, he can get you fixed up with a new or a good used freshly rebuilt clutch that'll be set up for specifically what you need.
 

GClary

Member
Where are you planning to race ? Finding a clutch person that knows the track is very helpful . Single disc clutch is more for smaller kids , what you are looking for is a good 2 disc clutch . 3 & 4 disc clutches are for big power engines . For the price , a good Stinger shoe clutch is also a good choice . A disc clutch is a better choice , because it doesn't get as hot when your idling around than a shoe clutch will . But they all have maintenance that needs done on them all the time , and a disc clutch is a little more complex than a shoe clutch . A disc is better on take off , but once both are locked up under power , there is really no difference that you would notice .
 

flattop1

Dawg 89
Hillard fury , simple , durable , inexpensive .
Stinger , durable ,slightly more expensive , special key still simple .
After that , bully six spring most expensive , relativly durable , more complicated .
 

spincycle

Premium User
I would go with a premier stinger drum clutch....not overly expensive $125 or so..vs a typical 2 disc which run in the $250-$300 range... that's for brand new mind you.... usually can find decent used ones on here for about half that give or take.... basic noram drum clutch is about $50 brand new if you want low cost...
 
Where are you planning to race ? Finding a clutch person that knows the track is very helpful . Single disc clutch is more for smaller kids , what you are looking for is a good 2 disc clutch . 3 & 4 disc clutches are for big power engines . For the price , a good Stinger shoe clutch is also a good choice . A disc clutch is a better choice , because it doesn't get as hot when your idling around than a shoe clutch will . But they all have maintenance that needs done on them all the time , and a disc clutch is a little more complex than a shoe clutch . A disc is better on take off , but once both are locked up under power , there is really no difference that you would notice .
Thanks for the information/explanation. Track is a 1/4th asphalt track in Alabama.
 
What’s the ideal rpms for the clutch? I see how I can change the springs out to to achieve lower rpms and vice versa. With the track being quarter mile asphalt would I want lower rpms? Should I go with lower rpms for better take off?
 

alvin l nunley

Premium User
My understand of things is a little different from most. I believe all clutches are pretty close to the same on the low end (except for the heat generated) it's on the top end where they're different.
Pete Mueller had an article on this subject, which explains it much better than I can. Still, notice how the direct drive engine turns more RPM than the clutch drive! Some of that is due to the fact that they run lower gear ratios, but it's my conclusion they also get more power to the axle. I have to believe it takes some power to do the things the clutch does. It's got to take some power to sling those shoes out against the drum. This means less power to the rear axle.
On the low end, where the clutch is slipping, heat is generated. It takes power to generate that heat, meaning less power goes to the rear axle. Less heat, more power to the axle. I have no idea if that generated heat has ever been quantified, it would be an interesting experiment.
 
My understand of things is a little different from most. I believe all clutches are pretty close to the same on the low end (except for the heat generated) it's on the top end where they're different.
Pete Mueller had an article on this subject, which explains it much better than I can. Still, notice how the direct drive engine turns more RPM than the clutch drive! Some of that is due to the fact that they run lower gear ratios, but it's my conclusion they also get more power to the axle. I have to believe it takes some power to do the things the clutch does. It's got to take some power to sling those shoes out against the drum. This means less power to the rear axle.
On the low end, where the clutch is slipping, heat is generated. It takes power to generate that heat, meaning less power goes to the rear axle. Less heat, more power to the axle. I have no idea if that generated heat has ever been quantified, it would be an interesting experiment.
I think this makes a lot of sense.
 

flattop1

Dawg 89
Something in the 3000 rpm range .
Maybe 200rpm more .
As a beginner the hillard with bully conversion is hard too beat overall .
 

Pete_Muller

Moderator
To the OP, my recommendation would be to first look at what the people winning in your class are running. That's *never* a bad place to start!

As far as clutches go -- if anyone is interested in discussing, it's probably best to start another thread and not hijack this one into a deep-dive into it. Suffice to say that there is a lot more to clutches than the "relatively simple look" of them would indicate. :D
 
To the OP, my recommendation would be to first look at what the people winning in your class are running. That's *never* a bad place to start!

As far as clutches go -- if anyone is interested in discussing, it's probably best to start another thread and not hijack this one into a deep-dive into it. Suffice to say that there is a lot more to clutches than the "relatively simple look" of them would indicate. :D
No worries. I’m trying to learn as much as I can
 

JPMKarting

Premium User
Go with a 2 disc/6 spring. Either a Bully or a Viper/Gator style clutch. They can be had for $100-$150 all day long, and will outlast the shoe clutches.

Engagement should be around 2800-3000 RPM for the Predator engine package.

I do have a freshly rebuilt Bully 2 Disc here in stock that I can setup for predator. It's a little pricier at $200 shipped, but it is fresh and built correctly.
 
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