Posted by ScottyHOMEy on April 08, 2009 at 07:01:59 from (70.105.245.98):
In Reply to: Magneto timing posted by Slappy on April 08, 2009 at 06:26:22:
You may mess up what you've already done by trying to time your mag the way you would a battery fired distributor. The timing job you did was to get the impulse coupler to trip right at TDC with the engine stopped. That's for starting purposes, and you don't want to wind up with that timing point advanced any or you run the very good chance of having it kick back and catch you when hand cranking. Same risk with advancing a battery distributor too far.
Now to your main question, as far as timing advance, speed is not an issue with a mag. It doesn't have the variable advance of a battery ignition. Timing is either at TDC when stopped or fully advanced when running at any speed. For that reason, you'll see folks around the board every now and then looking for a battery distributor for a puller -- they want the advantage of the variable advance that they can't get froma magneto.
If you were just going to check (or even fiddle if you decide you want to) the timing, I can't answer exactly. The H4 mag on your tractor lists a "lag angle" of 35*, which would be an AWFUL lot of advance. Full advance on a battery distibutor on a B would be 20* and you reach that at 800 rpm, so I suspect, where the mag is geared for the rotor to turn once for every two turns of the motor, that the 35* lag angle would translate into an advance of 17.5* when running. That's speculation and reason coming in on my part. Perhaps somebody will jump in to confirm or correct that.
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