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Bultaco M198 Crankshaft & Clutch Drum Removal


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Does anybody have any tips on freeing the crankshaft clutch sprocket and clutch drum nuts? I have the clutch holding tool but cannot free the crankshaft or clutch hub nuts with the engine on the bench (I dont have an engine stand). Should I (1) replace the cylinder, piston & head and lock the piston with a locking tool or, (2) replace the bottom half of the engine in the frame for greater leverage (3) do both. Without locking up the engine there is tendancy for the clutch holding tool to come to rest againt the gear selector shaft, which I feel needs to be avoided as I may risk damaging or breaking the shaft. My inclination is to replace cylinder, piston and head, put the motor back in the frame, dispense with the clutch holding tool, lock the piston and use a long socket bar for additional leverage. I cannot see how these nuts could release using just the holding tool and a regular socket ratchet, as pictured the manual. Any tips, tricks greatly appreciated.


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I don't want you to think that I'm trying to teach you to 'suck eggs' but often getting these undone is about technique as much as tools.

I've generally used an offset ring spanner for the clutch centre, make sure it's almost parallel to the handle on the clutch holding tool, so you can push the handles on each tool towards each other, sometimes using only one hand. This way you can apply a strong steady pressure without the motor trying to slide around. Works ok for the flywheel as well but not as easy, I have used some 'band type' oil filter wrenches to hold the flywheel and the same technique to good effect. If you're still struggling a bit of heat on the nut never hurts.........When you undo the flywheel work from the front of the motor, the clutch drum can do a fantastic job of removing knuckles if you slip.................

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