Many thanks to all who helped so far, particularly James
The one lesson I did learn is: try not to rebuild the engine, then try MS with fuel & spark at the same time. Maybe start with fuel. And in my case, I'm also running 6 VB921 with direct coil control. But at least most things seem to be functional now (still have to test/use the 2nd coil once I get another set of ignition wire for my twin plug).