The benefits of having studied calculus...
The chart below is to show an example of the complexity of the topic of ignition in engines. Folks ask what is the "ideal advance curve"? Most folks unfortunately don't even come close to understand and are stuck in kindergarten.
To fully understand how little you actually understand, if you think there is an answer without a full disclosure of all the information about the engine you are trying to apply a particular curve to.
Think of the grid pattern as moveable left and right within the colored nonlinear spacial plane. The intersection in one axis would be the cylinder pressure based on the throttle setting. The pressure would obviously change dramatically. The ignition curve is a fixed single plane concept around
RPM only and completely disregards throttle open, therefore disregards the pressure, cam selection, compression ratio, fuel, air temperature, engine temperature .
Ignition curves offered are by necessity default designed for WOT. That makes them very retarded for light throttle cruise. You are therefore slave to the curve you are given and the only setting you have is, where to set the curve in relation to the crankshaft... called initial timing. This chart is only to show "a complex nature condition" nothing to directly be norton or ignition related.
Anything is possible with enough effort, money and applied technology. The nortons are almost stone age in the sophistication of the ignition curves offered. As a technical comparison my Ram/CumminsTD 3500 which weighs 7700lbs has on occasion, gotten 27MPG. The computer controlled injection with the wide variety of additional supporting equipment to insure tremendously low NOX and HC emissions.
NHT do not have any sensors, except one, the rider who feels the kick back or hears the pinging . The advance curves are all below the WOT "ping point curve". Some ignitions may come close. Some are not to close and you loose performance. The dyno shows this performance loss across the band. Where individual engines can be tested and data accumulated improvements can be made.
Nov 1989 in the beginning my final conclusion
"My first Commando, bought new in July, 1970, was an unmitigated disaster. In September, 1987 I bought my second Norton Commando, a '72 Combat, and to insure some useful life for this motorcycle, I have been studying everything I can get my hands on. I've learned quite a lot in nineteen years, part of which is patience and skepticism, and part of which is the subject matter for this writing, that being ignition characteristics, primarily those of the Boyer.
snip
simple agreement with the concept that
one advance curve fits all is too much 'Black Magic' from the 'Black Box' for me to accept."
After 30 + years I now understand fairly well all the severe limitations of the ignitions applied to the wide variety of levels of tune of the NHT.
Feel free to go to my website and review in full @ the "information library"..."norton"...
http://atlanticgreen.com/boyerexposed.htm
http://atlanticgreen.com/boyerevolved.htm
We have obviously strayed from TS failure mode, to ignition suitability, and have gone to an immensely more complicated topic. frying pan into the fire.
If some intelligent person wants to start a new thread, I may comment other wise I'm leaving the sandbox.