h mipulse rotor

when the impulse mag trips does the impulse mag sent spark to the rotor before the rotor moves or as the rotor is already moving. in other words do I point the rotor directly at the #1 clip on the capjust before it trips or does the rotor travel as it is sending the spark ??

there are timing marks on the small gears, so that should make it right. The mag always fires when it points to the plug terminal it will fire. That point is not where it trips the impulse, it is when the magnet is up to speed and this makes enough primary voltage to spark the secondary when the point break, not away from that instant. Jim

The rotor is placed before the mag trips. i am not contradicting Jim's answer, although it may sound like it. I don't think you can set the rotor, nor is it necessary to set the rotor, at the exact place the spark occurs.

I have a little more time now, so here goes.
The impulse coupling is designed to trip at TDC.
This process initiates earlier in the rotation with a pawl that catches and holds back a spring.
The spring winds up for a given number of degrees of rotation. When it trips, the rotor is not pointing to the spark plug terminal. it is leading the terminal slightly.
The tripped magnetic rotor spins up to speed making current flow in the primary mag winding.
When the current is flowing at max, the points open. This occurs a little after TDC, making sure that there is no chance for kickback if the engine was hand cranked.
This breaks the current, and a secondary voltage is generated in the spark windings.
This voltage is directed by the rotor to the appropriate spark plug terminal (it is now lined up directly toward that terminal.)
When the engine starts, the mag impulse coupling is removed from action by a governor (speed sensor) that pulls in the pawl, preventing spring windup. This also causes the spark to no longer have the delay caused by the impulse system. Thus the spark timing is at full running advance.
IH mags of this type have no centrifugal advance.
I hope this explains a lot. The timing of the rotor is best set by timing marks on the little gears. Jim

If you turn it backwards, the rotor should be in the right place just as the points close.

If I remember correctly, if your mag is timed right, when you install it, the manual says to rotate it slightly to "trip" the impulse when you have the engine on TDC.

In other words, if the timing is correct on the crank, govenor and cam gears, set your #1 cylnder to TDP on compression. Install mag without tightening the bolts. The rotor should be pointed at #1 on the cap. rotate the installed mag to "trip" the impulse. You mag is now timed.