Re: OT - Fairbanks Morse FM Magneto timing

Posted by Glen in TX on November 07, 2005 at 12:31:54 from (65.249.225.109):

In Reply to: Re: OT - Fairbanks Morse FM Magneto timing posted by Jason Z in MO on November 07, 2005 at 08:48:24:

Jason, Let's back up a bit. Is this the original mag for the engine it was running fine with before? If so you may have some carb or fuel problems also. The old Marvel Schebler carb on those Wisconsins can give fits and the later Zenith carb is just better design. I have old BKN that runs fine with M/S carb. If the mag has not been changed and impulse has a snappy spring and seems to work ok and you got a good blue spark with clean points set at .015" would suspect something else. Impulse springs can get rusted and weak or break and impulse parts do wear or crack. Service manuals will also give specs for battery dist. ignitions used on Wisconsins and timing for those is simular and adjustable but not for the mags. Some natural gas or propane engines used as oil field pony engines may have had different timing. All the FM mags I see listed say 30 or 25 deg. and Wicos for AKN say 29,30 or 13 degrees. The bars forming the "X" on engine gear and mag gear should be centered in the timing plug hole and aligned when piston is at TDC. Piston should be at TDC with flywheel screen removed and the leading edge of flywheel vane marked X and DC are in line with the vertical mark on cover NOT the mark to the left of vertical. The mark to the left of vertical is for checking the timing of battery distributors which should be 28 deg. BTDC on a AK,AKN & AKS. Some other A models are 20 or 25 deg. BTDC as shown in a I&T manual LES1-4. Something else to consider is make sure the mag trips freely when on the engine. If you don't have a gasket or using silicone on mag you may need 1 or more gaskets to shim the mag drive out some also so the impulse will work properly.

Follow Ups:

• Re: OT - Fairbanks Morse FM Magneto timing Jason Z in MO 20:00:51 11/07/05 (4)
  • Re: OT - Fairbanks Morse FM Magneto timing Glen in TX 21:21:34 11/07/05 (3)
    • Re: OT - Fairbanks Morse FM Magneto timing Jason Z in MO 06:49:47 11/08/05 (2)
      • Re: OT - Fairbanks Morse FM Magneto timing Glen in TX 11:35:03 11/08/05 (1)
        • Re: OT - Fairbanks Morse FM Magneto timing Jason Z in MO 12:31:24 11/08/05 (0)

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