Magneto Timing Question

an impulse does not retard timing. while the mag is being spun slow your impulse will hold your mags rotor from spinning a while before TDC and let it go just before TDC. this quick action is needed while cranking slow to keep the points working accurate. if you had no impulse while cranking by hand, your ignition timing would be erratic due to the points opening so slow.

you might try checking your cap and rotor rotors position when you are on a cylinders TDC. your rotor should be straight accross from the caps post when your points are open. most mags point plate can be moved to adjust this.

Those are some pretty generic questions to cover all mags.....but in general
the AB & Eisemann mags are fixed timing (no advance) and the retard angle is fixed at 30 degrees.

The main purpose for the "impulse" is to intensify the ignition spark at low cranking speeds to aid in starting while minimizing the chance of back fire.

This is done by retarding the spark, stopping the rotor while winding up a spring and having the cam release the spring and rotor at the correct time to provide the intensified spark. Once started the mechanism returns the timing to normal at about 180 rpm.

So if your mags are operating normally other than at cranking, you need to look into the condition of the impulse mechanism, they do wear, stick and can get generally buggered up. They are also kind of touchy, depending on gravity, friction and sliding operation.
A weak impulse spring or fouled spring compartment can affect operation.

Whether it be AB, Eisemann or others about the only adjustment control is the setting of the "E" distance or "edge distance" on the AB or the timing of the induction rotor to the breaker plate on the Eisemann.

The "E" distance on the AB is the distance between the pole shoe and the edge of the magnet rotor.

If the distancing is off it will cause hard starting and loss of power.

Old Magnet,
Thanks for the reply. I understand what you mean about the rotor cutting through the magnetic field at the proper time when the points open (since both mags are fixed magnet and not rotating magnet). I haven't checked the point timing with respect to the rotor position but I can't believe it's too far off since it produces such a good spark. Back to my original question about impulse retard, you mentioned that most(all?) mags were set at 30 degrees. Have you ever seem one get worn such that the retard angle becomes greater that 30 deg.? I will try to measure the crank angle past TDC when the impulse clicks and compare to point opening crank angle with no impulse delay.
Dave