Understanding how the coil works on an onan 2 cylinder

[ejensen]

The cck Onan I have has conventional points and condenser. The coil has two wires coming out of it. One wire to one plug and the other wire to the other plug. How does this system work?
 

[Bob]

It is a "waste spark" system. Both spark plugs fire at the same time... one on it's cylinder's compression stroke and the other on it's cylinder's exhaust stroke (where the spark is "wasted").

The secondary winding is NOT grounded at one end or connected to the primary (as it is in typical ignition coil).

A lead from each end of the primary winding goes to to a spark plug. One fires with a positive-going pulse and the other with a negative-going pulse.

MANY automotive engine from the 80's up use the same type of system, having half as many coils as there are cylinders.
 

[ejensen]

Bob,

Thank yor for the information. A regular coil with one wire and primary wire to the points would not work, provided I understand your explanation.
Another question: Removal of the flywheel:I've used two pry bars and a brass drift to strike a blow with a hammer on the crankshaft nut. What is the proper type of puller?
 

[buickanddeere]

Deere also used the waste spark system with the gasoline starting engines from 1954 to 1963. Yes there were 840's sold until 1963.
The Deere two cylinder gasoline and all-fuel tractors also fired "lost spark" until the 20 series.
 

[LJD]

About your comment "A lead from each end of the primary winding goes to to a spark plug"

Is that a typo? I assume you mean the plugs are hooked to each end of the secondary windings?
 

[LJD]

I'm going to ask and continue in the "tractor talk" forum.

I've got a question about this system. Seems I'm not the only one. I was just reading a long discussion in a elec-engineerring forum and they were not able to answer a guy who has the same issue as me. I'm going to post the question over in the "tractor talk" forum where more might see it and get involved. Since it's used on tractors, motorcycles, autos, etc. and this audience for "stationary engines" might be a bit esoteric.