Re: tiller handle
There is a spring and a tapered friction plug up in the nose of the twist grip....or at least there is supposed to be one in there. That should be sufficient to make it stay where you put it.
If it doesn't, perhaps the coil is dragging on the flywheel magnets. That will shut it off in a hurry. Not only that, it damages the coil's laminated core. The laminated cores are supposed to be flush even with the machined edges of the posts upon which they mount.