[ERA535]

Andy -

Consider that the need for the intial timing to be where it is so that the thing will even start...

The timing doesn't just bang over to maximum advance then.

It has to be variable and dependent on rpm because of one thing:

The flame, once started, takes a set amount of time to burn completely. The faster the engine revs the less time it has to do that so it has to start earlier - this is called advance - and the faster the engine revs the more advance you need - up to a point.

Pat