Thoughts on Removing Flywheels and Keys

September/October 1996
Harold R. Keller 
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Route 1, Glouster, Ohio 45732

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Having been a reader of GEM for along time, it has become apparent that many engine men have problems with removing keys and pulling off flywheels without damage. Here are a few ideas that have worked for me, and may well work for others.

Gib keys, the ones with the little 'toe' can often be pulled with the aid of a shop made puller like the drawing. Measure the gap between the flywheel hub and the toe of the key, and use a piece of steel as big as you can fit into the gap. Make the puller as wide as practical. Cut a square notch in the center of this bar which will allow the bar to straddle the key. Carefully measure the spacing of the two draw bolts, and locate these as close to the key as practical, as a close spacing will lessen the tendency to bend the puller.

Drill, tap and fit up two fine threaded grade 5 bolts, using care to allow the bolt heads to pass a wrench. Locate the draw bolts in line with the bottom of the notch in the puller bar. This will locate the line of pull with the top edge of the key, and lessen the tendency of twisting out of the key on a hard pull.

When you have the puller made to your satisfaction, set the puller on the key, and hand tighten the draw bolts. Be sure the bolts bear on a flat part of the hub, as far as possible. On small or chipped hubs, it may be necessary to use a thin piece of steel as a bearing point for the draw bolts. If you anticipate a hard pull will be necessary, chamfer off the first thread to eliminate damage.

When you are ready for a trial pull, lubricate the bolt threads with grease or anti-seize, put a few drops on the end of the bolts and wind a strain on the key, taking care to keep the puller square with the key. Tightening the draw bolts will put a very strong, straight line pull on the key. If the key is too tight and will not loosen, generally no damage will be done, as the puller will bend before any damage is done to the engine. I have driven the key with a copper or brass hammer in an attempt to break loose any rust bond, and of course, soak the key with your favorite 'soak-them-loose' solution.

In extreme cases it may be necessary to heat the hub with an acetylene torch, expanding the hub a bit and possibly loosening it.

For keys without the jib, the problem is a little more spicy. First look on the inside of the flywheel and determine if a driver can be inserted into the keyway, allowing the key to be driven out from the inside.

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