Disc Clutch experts...

1fasttiller

Member
Looking for input, our team uses and sells Pulse racing clutches. We constantly have issues with them hitting hard and all at once, no gradual slipping. Fresh discs, spring heights are all set per Pulse, air gap is good. What causes that?

We only use a light smear of vaseline on the bearings per Pulse so as to no contaminate the discs with excess grease or any PTFE type lubes.

No extra weights used, and pressure plate is within spec and flat. Pulse wasn't much help to us...
 

alvin l nunley

Premium User
Gil Horstman once told me his biggest problem with the DXL was getting the cam shape right on the counterweights.
 

JPMKarting

Premium User
Looking for input, our team uses and sells Pulse racing clutches. We constantly have issues with them hitting hard and all at once, no gradual slipping. Fresh discs, spring heights are all set per Pulse, air gap is good. What causes that?

We only use a light smear of vaseline on the bearings per Pulse so as to no contaminate the discs with excess grease or any PTFE type lubes.

No extra weights used, and pressure plate is within spec and flat. Pulse wasn't much help to us...

Usually a hard snap would be caused by:

-Air gap too large
-Springs too heavy
-Too much lever weight
 

1fasttiller

Member
Usually a hard snap would be caused by:

-Air gap too large
-Springs too heavy
-Too much lever weight
Thank you sir, I'm confident our air gaps are to spec, and we use stock levers with no added weight so I'll have to look at the springs. I do think our crew chief puts a heavier spring in all our clutches.
 

Pete_Muller

Moderator
1fasttiller,

Does the clutch seem like it freewheels (as if it's in neutral) and then grab all at once? Once the clutch is "pulling", is the clutch slipping at the correct rpm? (possibly the gear ratio you're running makes clutch slip a very quick "event"?)

As JPM says, that is caused by a combination of springs, weight, air gap, and I'll add: which portion of the lever is contacting the pressure plate. Simply: if a lever is moving "further" because of its shape/geometry, it will "act" heavier.

If the clutch is currently slipping at the correct rpm, then putting weaker springs in will lower the engagement rpm, so something else will need to be adjusted as well to get back to the revs you'd like the clutch to slip at.

PM
 

Pete_Muller

Moderator
Gil Horstman once told me his biggest problem with the DXL was getting the cam shape right on the counterweights.

Al,

The lever shape on the early Horstman disc engine clutches were all done via "grind and try" method. Once Gil had something that he felt worked well, that shape was duplicated in a stamping die to make the levers.

PM
 
The "Pulse" clutch is Brian Barnes' version of the many Gator copy/style clutches.
He's a good guy, I'm surprised he couldn't help you.
You might inquire with Mike Curry about it and see if he can recommend some things for you.

It sounds like too large of air gap, or even the wrong levers, but it's almost impossible to tell for sure what's going on without seeing it on my bench.

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
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