Grabbed this from a site
If you want to swap the EC transistorised engine into a ZABCD bike with CDI ignition, this is what you have to do:-
You can retain the following from the EC bike : engine centre section complete, with automatic cam chain adjuster; engine front section with clutch.
You will need the following from your CDI bike : radiator, engine a-frame (front hanger), gear lever; rear engine case complete; alternator rotor; stator complete with harness and advance pulsers. The EC rear case does fit the ZABCD engine but as it's longer, it will foul the water bottle.
You cannot swap the manual cam chain adjuster for the automatic type, or vice versa.
Offer up the ZABCD rear case to the EC centre section and very accurately mark where large 14mm black auto tensioner lock bolt hits the inside of the rear case. You can either (a) machine off half the depth of the bolt's head or (b) enlarge the manual tensioner locknut hole to accommodate the bolt's head. Either way, seal the hole afterwards, from the outside, using plastic metal.
You MUST use the ZABCD alternator rotor with the brass timing plug, as the advance pulsers on the CDI stator harness depend on this to work.
Check out this site for info. sometimes it has the answers faster than asking them here sometimes it doesn't have any answers.
http://www.elsham.pwp.blueyonder.co.uk/cx500/engineswaps.htmlhttp://www.elsham.pwp.blueyonder.co.uk/cx500/