Eiseman G4 edition 3

[Jim Ryan]

I have a Continental J4 engine running an Eiseman G4 Edition 3? magneto.

I can find information on the G4 and the G4 edition 2, but no mention of an edition 3.

My magneto has no provision for manual spark advance.

Could this be theautomatic advance Eiseman or am I just missing the advancemechanism?

The mag is hot and the engine runs fine at idle.

Any help would be appreciated.

[keith1944]

The Eisemann G4 magnetos were set up at the factory with either a fixed timer or a variable timer. Changing from fixed to variable requires a different timing lever, moving the stop pin, and most likely resetting the distributor disk.

[Dempster]

G4 3rd Ed. has a IS-5 automatic impulse drive for starting retard then when starts speeding up throws the impulse out pawls out by centrifugal force to quit tripping. G4 3rd for Caterpillar uses IS-6 impulse. If impulse trips then the spring is good and if it throws out like should it's fine and not worn. 2nd edition has dist cap that clips on with wires out top. 3rd edition dist cap mounts with 3 screws and had horizontal towers for wires. On 3rd Ed. caps the brush must be removed to loosen the pointed screw behind it to change out wires. Most other parts interchange between the 2nd & 3rd edition G4. 3rd edition was just improved some suppose to be more dust proof and later 3rd editions had no provisions to oil the armature bearings just being grease packed with high melting point grease. The 3rd edition was not made in the 4/2 version for 2 cylinder engines however the 2nd Ed. was. There is a different method to time the variable spark G4 3rd Ed. than the fixed spark model like you have.
G-4 2nd & 3rd edition fixed spark timing is done by having the #1 cylinder at TDC compression stroke. Then loosen coupling bolts turning mag in opposite direction of drive aligning the mark line on dist rotor disc with the pointed indicator screw at the top then tighten bolts up and should be timed in the advance position.

[Jim Ryan]

Thanks very much for all the info. My mag has the provision
for oiling the armature. Do you know what years edition 3's were produced? This engine is in a 1922 truck.

[Dempster]

Probably mid or late 20s and 30s ? Not sure or around my Eisemann book tonight or if it did have any dates on parts sheets. On Edition 3 parts list it had it broke down by serial numbers of changes on them. There was a GV4 and CM series too before the later Eisemann AM series replaced them.