Bully clutch


New member
I'm attempting to build bully clutch for the first time.. It's a 2 disc, 6 spring with red springs.. I understand most everything I've read about rebuilding one..
My question is, what are they calling stall speed? Is that the rpms where the clutch is fully engaged?
Any help would be greatly appreciated..


Premium User
That will be the rpm where you want your clutch to lock up or come in at. Unlike shoe clutches these don’t have a lot of chatter before lockup. Follow the guidelines Buller lays out for you and it will work fine.

alvin l nunley

Premium User
I ran the first ever Horstman disk clutch at a Nationals at the Atwater California IKF Nationals in 1977. What I called these things then probably is valid now.
Engagement; when the clutch first starts contacting the discs.
Stall; what the tachometer is reading coming off the corner. When the engine and the axle, divided by the gear ratio, are not the same
Lockup; when the clutch and the engine, divided by the gear ratio, are turning the same RPM.
I.e. gear ratio 4 – 1, engine 12,000 RPM, axle 3000 RPM. That probably occurs at a point sooner than 12,000 RPM. And that of course depends a whole lot on a whole bunch of things. Stall should be at the point in the RPM range where the engine is producing maximum torque. In my opinion, no other point in the RPM range will give you as much acceleration out of the corners. Maximum torque at the axle means maximum HP at the axle, means maximum acceleration. If you need any clarification on any of this, let me know.

P. S. "Lockup" no ( noticeable) movement between the discs and the pressure plates.
Last edited: