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MC How-To

Step by step: From general maintenance to complete restorations, we share tips and tricks for working on classic bikes.


DIY Norton Clutch Hub Compressor

Our homemade Norton Commando clutch hub compressor tool (at right) next to a factory tool. It may not be as sleek, but it works just as well.

If you’re servicing the clutch on your Norton Commando, a clutch hub compressor tool is a must. The Norton Commando clutch is a simple, robust design utilizing a single diaphragm spring to clamp the clutch plates together. Although factory-style clutch hub compressor tools are readily available and reasonably priced, (typically $25-$45), if you’re like us you get a certain kick out of making your own tools when you can, and this is one tool you can easily make, usually for less than $10 if you already have much of the hardware sitting around, as many of us do.

To make the compressor here, you’ll need:

• 1 x stick of fine-thread 1/2-inch all thread or a 5-inch 1/2-inch threaded bolt
• 1 x 1/2-inch bolt washer
• 1 x 1/2-inch fine-thread steel (not nylon insert-type) lock nut
• 2 x 1/2-inch fine-thread nuts
• 1 x 4-inch PCV pressure cap
• Medium (blue) thread-locking compound

Here’s all it takes to make the tool: a 5-inch OD PVC slip cap (shown here with center hole already drilled), a 5-inch bolt or piece of all-thread, and a few nuts and washers.

Making the compressor is simple.

• Take the PVC pressure cap and drill a 1/2-inch hole directly through the center of the cap. The pressure cap we used is rounded at the top instead of flat. You can use a standard slip cap, which is flat at the top, but we like this type better as it’s a little stronger. If necessary, trim the cap to an overall length of 3 inches. The cap we purchased was already at this dimension.
• Cut a 5-inch piece off the all-thread stick or use an existing 1/2-inch fine-thread bolt, making sure the threads are clean and serviceable.
• If using all-thread, thread the two standard nuts onto one end of the all-thread and then tighten them against each other to lock them in place. Clamp the end threaded with the two nuts in a vice to hold it firmly. Apply locking compound to the other end of the all-thread, then thread the steel lock nut onto the all thread until it’s fully on engaged on the all-thread and locked in place.
• Loosen the two nuts you jammed together. Remove the lower nut, then thread the upper one up to the lock nut. Install the washer under the nut then insert the threaded shaft through the top of the PVC cap. Thread the second regular nut onto the threaded shaft. That’s it; you’ve made your Norton clutch hub spring compressor.

Drill a 1/2-inch hole through the center of the PVC pressure cap. If necessary, trim the cap to an overall length of 3 inches.

Cut a 5-inch piece of 1/2-inch fine-threaded all-thread (or use a 5-inch bolt if you have one). Clean the threads and apply locking compound to one end.

Lock two regular nuts to one end of the all-thread, lock the piece in a vice, then thread the steel lock nut onto the all-thread until it’s fully engaged and locked in place.

Release the two regular nuts. Remove the lower one, then thread the upper one up to the lock nut and install the 1/2-inch washer.

Insert the center bolt through the PVC cap and thread the second regular nut onto the center bolt.

The homemade spring compressor assembled and ready to work.

Using the clutch hub compressor

To use the tool, remove the center adjuster screw from the clutch diaphragm spring hub. Place the clutch hub compressor loosely over the diaphragm spring. Thread the clutch hub compressor center bolt into the diaphragm spring hub, making sure at least five of the bolt threads are engaged in the hub. Jam the nut on the clutch tool center bolt tight to the spring hub. Next, hold the clutch hub compressor bolt while tightening the standard nut against the washer and PVC cap. As the nut is screwed tighter the clutch diaphragm spring will be pulled flat. Tighten slowly until the diaphragm spring releases and spins in the clutch hub. Remove the diaphragm retaining circlip, followed by the diaphragm spring.

To use the tool, remove the clutch hub adjuster screw then screw the clutch hub tool into place making sure at least five threads are engaged in the diaphragm spring hub.

Jam the lower nut against the diaphragm spring hub to lock the center bolt in place.

Hold the center bolt and tighten the outer nut until the diaphragm spring pulls flat and spins in the clutch hub. Remove the diaphragm spring circlip.

The Norton clutch diaphragm spring removed.