The GS series was a medium duty line similar in construction to the larger G series. They were well made and quite hot. They often used a mica condenser that was nearly immortal, strong magnets, and robust breaker points. They suffered from the ravages of neglect,dirt,gooey insulation, petrified grease and crumbly potmetal, especially the breaker housing. They used some special pitch metric threads and the plug wire did not simply plug in (That would be too easy!)See the discussion below. These images are from an early Eisemann owners brochure. The image on the right is for the early version. Both are nearly identical. Some used two clips to retain the distributor and different post arranngement.
The GV and GS series used a lot of 4mmx.75mm threads (Not the standard metric 4MMx.7) inside for their safety gap screw, timing pointer,armature end caps and 10-32 threads on the outside. There are also metric threads lurking in some of the later Eisemann magnetos as well.
There were two or more versions, appearing in the mid to late 1920's.
Remember to connect the stop switch for safety's sake.
See how the plug wires are fastened. Some versions like this one described in the manual don't simply plug in. We must carefully pull out the brush and spring with a quick twist so not to distort the spring, then poke the stripped end into the hole and tighten the setscrew. If you look inside the cap, often is scrawled something like "Strip cables to 1/2" or 11/32 or 3/8 depending on the model. If the mag got too much Oregon Rain and the steel setscrew seizes in place as happens a lot, make a drill bushing that fits the brushholder center drilled to the tap drill size for a 10-32 or whatever the thread is. Hopefully you will get at least one screw out to measure.
If you take the armature apart, the screws in the ends are 4MMx.75, not the more common 4MMx.7 metric size.
If the mag has fixed timing and a potmetal sleeve holding the stationary cam lobes, beware of suicidal potmetal. The sleeve often swells up and distorts, causing the cam lobes to be asymmetric and not fire evenly, or crumbles away.
The points should open every 180 degrees of rotation if all is well.
If it slightly distorts and the potmetal is fairly stable, very carefully dial it in straight as possible in a 4 jaw chuck and bore it straight to then reinstall the cam lobes with a circle of shimstock to retain the original factory bore size. If you bore it out .020, use .010" shimstock. If the sleeve is not sound, find a bronze bearing with an inside diameter close to the right size and bore to size to make a new sleeve. Beware of special pitch metric threads on this critter!Be extra carefull with the cap hold downs that thread into the fragile potmetal housings with the special pitch metric threads.
When they are in any state of repair, they are quite hot and reliable in spite of it all.
The bad news is that your magneto is probably out of warranty. The variable timing assembly was usually cast bronze or iron and not a problem. If the mag application is a fixed timing installation and a variable timing mag is available or the cam sleeve bad, set the manual timing to maximum advance and the time to the engine such that the impulse snaps at top dead center.
If you find a factory authorized Eisemann dealer, please let us know!