83 750 with week spark

Working on a project, it has spark but weak. I tried wiring in a spare coil, but no change.

Any guidance on where to look?

 

check battery voltage first.

 

You may also have some corrosion in a connector, I had that on my ST1100 on the red connector which feeds power to/from the right bar switches. Low voltage at the ECU as a result.

 

Check your terminals and connector to the coils, mine were corroded on my 83.