Take the disc off, engine off the base and clamp the boss on the crank in a vice.
Or if you dont want to take the engine off the base, refit the head with something in the bore, small block of wood perhaps, soemthing not sharp that will spread the load so as not to damage the piston or head.
The old trick is to feed a bit of clean rope into a spark plug hole. Then rotate the motor to lock it. I actually used this trick a few months back to get the harmonic ballacner undone on my father in laws little suzuk swift. worked a treat, should have just done that to start with instead of chasing around after a compresor and rattle gun that wouldnt even touch it.
Shouldnt take much more than 10mins to pull the motor right off, and if youve got a vice this is the go.
Then for when you need to turn the crank but still want to hold the engine in the vice, get an 8mm bolt and cut the head off hacksaw a slot in the shaft so you can screwdriver it in and out and use the stud in a mounting bolt hole and clamp that in the vice. Dont take the stud out, use it as a guide pin to put the engine back on the frame, only take it out when you have a couple of the other mounting bolts back in.
You can actually reassemble the whole motor, ignition starter etc and test it for spark in the vice, then put it back on the mower, add carb, test the stop wires and its good to go.
I do it this way for mowers with ignition module issues.
Cheers, Bob.
