A few years ago I was sitting chatting with one of the mechanics in the old Marlboro Roberts team as he worked on the bike. He was putting in a new crank after practice The rattle gun had been used to pull it apart and I said nothing up until he put the ignition rotor and primary gear on again with the gun. "Is that ok for the crank?" I asked, "That'll be alright" was his reply. He then proceeded to torque it all up.

Hmmm. Having spent more than a few hours truing cranks up I know full well how easy it is to move a crank flywheel just a fraction which is more than enough to turn an engine from a smooth high revving beauty into a vibrating animal.

My advice is to use the rattler as a last resort, or if you don't intend to use that particular part again.

That's my theory anyway and I'm gonna stick to it.