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littlemarv

Coils, condensers, etc.

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littlemarv
Does anybody know how much resistance there should be on the small wire that goes to the coil on a Briggs 23D? I have .4 ohms which is virtually nothing. My thoughts are the coil is just that, a coil of wire, but should it have continuity to ground? I have intermittent spark at best, and it barely jumps an 1/8" gap. And I always have ground at the insulated terminal on the points cover. When I remove the coil wire, then the terminal loses ground when the points open. I have an automotive coil and condenser, hook them up and I have spark strong enough to jump probably 3/8" in my spark tester. I'm kicking myself because when I pulled the engine 3 TIMES I never remembered to check the gap between the coil and flywheel. Could too big of a gap or rust cause weak or intermittent spark? Or is the coil just shot? A small engine guy told me coils don't cause weak spark, they either work or they don't. At any rate, I'm going to hook up my external setup for now, put the tractor and attachments through their paces, then check on the coil when I tear the tractor down for restoration. The condenser I got with the automotive coil is too big to fit under the points cover. Can I mount the condenser with the coil and just hook the condenser to the negative terminal on the coil? Or does it need to be physically near the points? What exactly does the condenser do?

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RayS
Not sure if you have read the link below, but there is a lot of good information. You will need a new ignition switch as well. I have had success removing rust from the magnet on the flywheel. http://www.simpletractors.com/do_it/magneto_to_coil.htm

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powerking_one
Ryan, The Briggs 23D series of engines use a "Magna-Matic" type of magneto system, and as I recall from others having weak spark with these, the coils are very failure prone. My brother had one on a generator; it would start & idle OK, but once it got warmed up it would not rev up and just die. He replaced the coil and issue was fixed. The primary winding side of the coil resistance is in the .2-.5 ohm range. If there is short between the primary and secondary windings, this could definately explain the behavior you are seeing. To eliminate the condenser being at fault, you could temporarily mount the other one externally of the points box. Air gap of the coil to flywheel should be in the .011"-.014" range (you could use a standard business card for this). The condenser counteracts the inductive current from the coil and minimizes arcing of the points. The coil/condenser is a "tuned" circuit in electronic terms. Tom(PK)

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