heres a pic of my 24cc echo wich i cut the center out of the flywheel,the large ring at the back of the prop hub wich holds the magnet.then the prop hub is screwed onto the flywheel cut off.Tim is right,i have 2-3 cutoff cranks that i use as mandrels to hold my flywheel sensor.And after looking at my hubs i have an extra one that would fit your threads but you will need a flywheel center to mount it if ya wanted to go with EI.if ya wanted to just use the mag then youd just screw this onto the flywheel as is.your only going to loose about 8oz with EI.ill send ya a PM.the hub i have xtra looks just like the one in the pic.