Lock the shaft? Why? The electric PTO clutch is bolted on to the shaft of the motor. First remove the bolt in the end of the shaft .It has a key way so it WILL not turn on the shaft. It is not screwed like a chain saw clutch. You remove the bolt and with any luck you will be able to pull it off the shaft. The problem comes when it gets rusted on the motor shaft. Clutches that I have known for a fact were no good and were trash I have had to destroy to remove. If the PTO clutch is still good it can be fun to get off some times. DO NOT use heat on a clutch you plan on reusing because it will melt the coil and destroy it. Always use anti-seize compound when putting on a PTO clutch. You can not even use a puller on most of the clutches with out destroying them. If you have a stuck PTO clutch you wish to remove and reuse go get a few cans of WD-40 and pray. Good luck
"DEFECTIVE OWNER/OPERATOR NOT COVERED UNDER WARRANTY"