Thank you Peanut. I thought the vacuum variation with throttle position might not be reliable enough, but cars did use it for years. I guess advance mapped against rpm is the real answer but a more complex design issue for me to tackle.
I was gapping my plugs .080 back in the seventies,open'em up till it misfires or performance drops. On worn out plugs you'd see .100 plus and still firing away. The HEI is a damn good ignition system.Oh, that's nice. I knocked up a twin-HEI unit for my Suzi GS a couple of years ago, using the standard ignition triggers and mechanical advance. It worked well. Never tried the extreme gapping, though. A google for "HEI ignition for Kawasaki" will find the site I got the info from.
I've been eyeing the Microsquirt ever since I followed your build Ratranger. To say I'm envious would be an understatement... Do you know if the 80 and up TCI triggers are compatible with it? I can't seem to find a definitive answer, but it looks like they would be.You really need either MAP or TPS, preferably both. The basic way the microsquirt works is you have the ignition table, bottom is RPM, side is load. Load can be MAP, or TPS or a combination. So the advance is based on load and RPM. Simplest is to start with TPS and RPM also known as AlphaN tuning. Then you can datalog and see what your vacuum signal looks like and incorporate it if you want.
Here's what a basic ignition table looks like.
View attachment 149517
Not mine, I've basically got the stock advance curve in mine, 13* at idle and 38.5* at max.
Actually the TCI has two triggers.... one for full retard and one for full advance. And that's what makes me think it will work.1 trigger every revolution is not good accuracy.