The Eisemann 72D was used extensively in the Maytag twin engines. They share many similarities to other Eisemann flywheel mags. Maytag also used a model 72D A Eisemann that looks identical to the 72D but the flywheels and armatures are not interchangeable but used the same points, coil,condenser and backing plate. Makes no sense. Possibly went to a larger flywheel magnet and decreased the radius of the poleshoes. The flywheel on the 72D has a larger inside diameter and the center pole shoe of the coil assembly is about .070 taller than that of the 72D A. Very annoying indeed Mr Eisemann. More on this one to follow. When testing for spark, always have one plug lead grounded or connected to the other plug. Never crank engine without the plug leads connected to the plugs or grounded lest you damage the coil. These coils are difficult to make and spendy. Service info is similar to other Eisemann flywheel magnetos. Spark plug gap is .037" unlike most specifying .025". Condenser is a .15 Microfarad device. We hope this helps get your laundry washed. The test procedures for the 72D and 72DA are the same.
For some reasin there is not much info in the 72D and 72DA in the Eisemann literature. More information can be found in maytag service info. Fortunately they both use the same coil,condenser and backing plates.
The coils can be annoying and expensive. The best way we know to test is with an actual Eisemann coil tester of the day. It uses 2 spark gaps and pulses the coil primary through a set if points and condenser and measures the current required to get a steady spark at both gaps. If the current to fire both gaps is below the max for that particular coil it is a pass. The converse is true. resistance measurement across the high tension terminals is of limited utility. It will tell if the coil is open(broken) inside and is a dud and will not assess the condition of insulation/leakage inside the coil. Most coils that are not broken will work unless they have moisture inside. Unless the coil is defective it is best to leave it on the poleshoe.
Here is how the coil under test is connected to the Eisemann winding tester. One primary lead (black clip) goes to the coil ground and the other (red clip) connects to the points with a piece of paper between the contacts. Since the magneto has a built in condenser the condenser switch on the lower left of the tester is turned off. The spark gap leads are connected to the plug wires. The knob in the center obscured by the plug wire is adjusted to slowly increase the current till both gaps fire steadily.
The maximum current for the coil stator assembly for the 72D and 72DA is 1.9 Amps
This coil easily fires both gaps at 1.4-1.5 amps and is a definite pass.
The condenser P/N H20-549 can be an issue with these as they like many of the day can develop electrical leakage and cause a wimpy spark. Fortunately Mr. Lawnboy has an excellent remedy. It is the correct capacity, mounts similarly and is readily available from parts jobbers. It fits earlier Lawnboy products and may be known as 31-1800 or 1800 or 677299. This also works with the later 72DA.