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With the engine running, you will be looking for fire at a point approximately 30� BTDC and not at TDC. Perhaps this is why you didn't see it (PatB) EXCERPTS FROM THE JD-H RESTORATION GUIDE - - - MAGNETO TIMING LAG ANGLE -- The lag angle or impulse range is the angular amount of retardation in timing between a magneto at cranking speed and one at running speed. The drive cup installed and the impulse stop plate adjustment are the factors that determine this relationship. For the JD H, this angle is set at 30 degrees. The drive cup determines the running timing, and starting (also called impulse) timing is adjusted by the position of the impulse stop ring on the drive cup end of the magneto. NOTE: For gasoline operation, the trend is toward a 25 degree lag angle. All discussion herein will state 30 degrees. STARTING TIMING should be very close to TDC. Some observers say that an advance of several (not more than 4) degrees BTC makes easier hand starts for the early JD tractors. Others claim it makes starting more difficult and is especially hard on a starter motor. Starting timing is easy to detect. No instrument is required. It occurs as the magneto sounds with its familiar "snapping" click. RUNNING TIMING -- The amount of advance BTDC is determined by the specific drive cup installed on the magneto. The switch from starting timing to running timing is an automatic function. Running timing is the result of the specific drive cup installed and the position of the magneto on the tractor. Rotate the top of the magneto to the rear for more advance, and forward to reduce the advance. The "rotating" action or phenomenon is similar to loosening the locknut and rotating the distributor on a '57 Chevy. For those adept in timing light use, this adjustment can be performed on a running tractor! See "Timing" paragraph below. PERFECT TIMING -- If you have a timing light and know how to use it, establish a reference point on the tractor for TDC. Then mark the flywheel at 30 degrees BTDC in relation to the reference mark. Start the engine and set timing by rotating the magneto forward or to the rear. Next, scribe two index or registry marks, one on the magneto flange and the other on the governor housing. In-register condition of these marks represents your running timing. Stop the engine and remove the timing light. Rotate flywheel forward slowly, observing when the impulse occurs. If it is at TDC, you are finished! If impulse comes before it should: remove the magneto, loosen the four screws securing the impulse stop ring, and rotate the ring CCW ever so slightly. Reinstall the magneto ensuring those two new marks you made are in register and check your impulse timing again. Repeat this process of trial and error until you achieve the impulse timing desired, then secure mechanical and electrical connections. This procedure represents the proper method to achieve perfect magneto timing at the factory-specified 30 degrees BTC for running conditions, and the ignition timing for starting is as TDC. ++++ If you want more, write me -- my email is open. Also, you can read a bit about JD-"E" systems on the JD-H Restoration Site (below), scan across to ARTICLES 1, and then from the drop-downs, select ELECT SYSTEMS. (PatB)
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