What would a higher rated ohm magneto actually do?


Active Member
Local time
7:49 PM
Jun 3, 2023
the great state of New York
Something scrolled across my screen just now, and let's chat about these higher ohm magnetos.

My thoughts? Pointless.
Have I owned one to have this opinion? No.

Circa 2008-2010, the magnetos that came in the kit were rated for around 400-450ohms and they were blowing CDIs. Specifically, Don Grubee then went to a 250 ohm mag but the engine would have a hard time starting. The 320-350 ohm range appears to be the sweet spot for these.

I don't doubt the magnetos themselves are the ohms they claim to be. What concerns me is the CDI though. I have found two different vendors who sell these fat magnetos and state there is a "high performance CDI" that goes along with it. However I don't think it can be ignored that these "high performance CDIs" are in the exact same casing as a stock one, almost as if it is.

I just bought the Parmakit CDI that has a retarded ignition curve at higher RPMs for my saw. I would say the magneto would handle just fine with that CDI. On a stock build, I genuinely can't see the point in a higher ohm rated magneto. I'm not sure what performance gain people expect other than a stronger spark, because if the spark is stronger, that results in what outcome then?
I run the Parmakit cdi on a stock magneto.. Minarelli conversion engine.
It produces a very noticeable and positive effect on the mid range.
The engine gets up on the pipe much sooner.
To answer the question presented: OHMS is a measure of resistance. More resistance in the magneto's winding can only be caused by two things. A smaller wire gauge or more turns of wire. Assuming the wire gauge is the same, more turns of wire will produce a higher output voltage. Mismatching the resistance of your magneto to the CDI most likely will cause you problems, unless you really understand the parameters of the CDI circutry you're dealing with. CDI schematics and specs are all proprietary and all but impossible to obtain.