There are a number of ways to accomplish the compression of the Clutch Diaphragm Spring.
Some of which rely on the clutch adjusting screw (ramp assembly stud) to pull against to compress the spring.

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3“ PVC cap w/ 5/16”x24 bolt or all-thread, coupler, nut and washer.
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However, if the pressure plate is cracked / broken or the adjuster stud can't be otherwise used, below are some other ideas to compress the assembly.

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Also, here is a commercial compression tool modded for use without the adjustment stud.

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