John Deere H installing magneto

[Bill Small]

Where can I find instructions for installing a magneto on my H?

 

[F-I-T]

Page 34 and 35 of the operating manual OMR2011. Pictures and everything.

 

[dan_41jdh]

Bill,

I stole the information below from the late Pat Browning's website under "Articles 1" and "Elect Systems":


1. Remove No. 1 (flywheel side) spark plug. Bring engine to No. 1 at TDC of its combustion stroke as indicated by pressure build up. Flywheel L.H. Impulse should be at its timing mark, or at 3:00 oʹclock. The slot in magneto flange on governor shaft should be horizontal.

2. Secure a short lead into the upper terminal of magneto distributor. Hold magneto in the same upright position as if it were mounted to the tractor. Gripping the drive lug on the impulse coupling, turn coupling to the left (CCW). Stop immediately when impulse occurs and spark occurs at the inserted lead. The driving lugs on the magneto should be in horizontal position.

3. Replace magneto and its gasket onto the governor case, being sure the driving lugs of the magneto are engaged into the magneto flange on the governor shaft. Hand-tighten fasteners and rotate magneto top forward as far as it will go. Rotate flywheel (top forward) one complete turn and line its L.H. Impulse mark with its timing mark, or at 3:00 oʹclock.

4. Tap the top of the magneto toward the rear of the tractor a small amount at a time until the impulse trips. BE CAREFUL - TRY TO NOT OVERSHOOT.
NOTE: If you do overshoot, return to step # 3 above and retry.

5. Tighten the cap screws holding magneto and install spark plug cables. Ensure the flywheel side plug is connected to the upper magneto distributor terminal.
Link

 

[dan_41jdh]

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[Anonymous-0]

The easiest way is just bolt it on. If it backfires when you crank it over, it's 180 degrees out. Remove the mag, rotate the drivelug 1/2 turn and reinstall. Set the impulse then to click when line on flywheel is at 3 o'clock position.

 

[John T]

The other good gents have ya on the right track. As long as the mags drive coupling mates into the open female slot in the govenor shaft its either gonna be close or 180 out. If its 180 out a top n bottom plug wire swap makes her run if its a Wico C or X or other direct drive (NON gear reduction) Mag. However I prefer the factory original setting where the top tower fires the left cylinder. Pats procedure gets it right the first time as I recall because he hand trips the mag to where No 1 just fired so 180 later 2 fires.

Then you can loosen the bolts and rotate the mag forward CW to retard or backwards CCW to advance the timing. The static start impulse timing needs to be right at TDC and the run time advance is mostly a function of which drive cup is used (like say a 25 degree) followed by rotation of the mag and its points gap and wear n tear.

I set the static start impule timing right at TDC then slap a light on and so long as the run timing is 20 to 30 (I prefer 25 BTDC) I let her go. My departed friend Duane first set the run timing usign a light and then went back and adjsted the rear stop plate to get TDC start timing.

John T