Stall vs Engagement vs Lockup

B

BradHickman

New member
I've seen stall, engagement, and lockup used to suggest clutch adjustment. Years ago when running two strokes we would lock the brake, open the throttle call the rpm reached "Stall Speed". I'll be using a 2 disc Bully and their charts list Stall Speed. Could someone enlighten me on what Engagement and Lockup are vs Stall speed?

I'll be running a stock Predator class that allows any exhaust and air filter. From what I've read on these forums the clutch should be set around 3000 rpm. Does that sound about right?
 
All of the above are the same thing. What RPM does the clutch fully engage at is what matters.

Predator stuff is 2800-3200 depending on weight.
 
Brad,

As JPM says: those 3 words refer to the same thing... "generally speaking".

There are nuances to how a clutch slips and engages though...

For instance, the materials used for the friction surfaces (whether discs/floaters/pressure-plates, or shoes and a drum) virtually always have a different "dynamic" coefficient of friction than the "static" coefficient of friction. Most 4-cycles are using dry clutches, but there are also oil-filled clutches often used on 2-cycle engines (unless a jackshaft is used). Temperature can also effect both the static and dynamic coefficient of friction (probably dynamic more so). This may be important to consider if/when running slow parade laps.

Additionally, the amount of spring and weight in the clutch can change the engagement characteristics (even if the stall RPM is exactly the same). Too much to get into in this short message.

If you are fairly new to the sport, the best way to go is simply get a recommendation of what clutch(es) work well, and how it should be set up to get you very close to the recommended "stall speed".

PM
 
Good answers above, Brad.

In addition, I add the term, "chatter engagement." Some clutch manufacturers (particular drum clutches) refer to their engagement rpm as to the point where the shoes first make contact with the drum. I feel that this is misleading as the clutch is not particularly "engaged" at that rpm, simply starting to engage. If the clutch has enough engagement to start to rotate the clutch drum/basket (possibly even the rear tires on the kart stand,) isn't what I call "engagement." That is chatter engagement. Actual engagement is generally 4-500 rpm above that depending on the clutch design, air gap, coefficient of friction, etc.
Clutch engagement should be at (or very near) peak torque of your engine. If your engine has been on a dyno, you will know exactly what rpm to engage your clutch.

To answer your question on engagement, yes, 3000 rpm should be very close for your application.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
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34 years of service to the karting industry ~ 1Cor 9:24
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BradHickman said:
I've seen stall, engagement, and lockup used to suggest clutch adjustment. Years ago when running two strokes we would lock the brake, open the throttle call the rpm reached "Stall Speed". I'll be using a 2 disc Bully and their charts list Stall Speed. Could someone enlighten me on what Engagement and Lockup are vs Stall speed?

I'll be running a stock Predator class that allows any exhaust and air filter. From what I've read on these forums the clutch should be set around 3000 rpm. Does that sound about right?
Click to expand...
Yes that is correct 3000 call me sometime and I will explain if
ph 27056;1507
 
torque peak of a box stock predator is around 2700-2800 (I've had more than a few on the dyno) thinking there is any advantage to setting it at 3000 or maybe 3200 is a common mistake made amongst Karters. too many times I've pushed or passed karts with poorly set up bullys with a properly set of shoe clutch. more rpm is NOT better. in fact its putting additional wear and heat into your $$$ clutch. . best to get it on a dyno and set it right.
 
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