Main Motorcycle: 77 Bonneville
Join Date: Jul 2004
Location: Melbourne, Australia
You've done all the regular checks, and if you get spark when you touch the b/w and b/y wires together, your Boyer should be OK.
What kind of spark plug leads and caps are you running? If they're suppressor leads or caps, you'll have problems getting a decent spark with the 2 x 12V coils. Measure the leads and plug caps - disconnect from coils and plugs and measure resistance end-to-end. If more than a few ohms (eg if they read 5Kohms), then they are suppressor leads. If you're going to stick with 12V coils, try copper-core leads, and non-suppressor caps. If you already have copper core leads and straight through caps (no suppressor resistor inbuilt), then go for the 6V coils.
I had similar issues using 12V coils and Boyer MkIII, with copper leads, and as soon as I went to 2 x 6V coils, my issues went away.
What plugs are you running? Again, if they are resistor plugs, replace with standard Champion N3's.
Per Ardua Ad Astra
(Through difficulties to the stars)