ignition coil gap opinions

S

slomo

Lawn Pro
We've all heard "just use a business card" for setting coil to flywheel gap. Just measured one I had laying around. Came in at 0.015".

Most of MY older Briggs take 0.006" to 0.010". Looks like I will be regapping tonight.
 
I've seen some plastic cards that a .020 and more.
I now make sure that I'm using the 8-.010 types, but I've not noticed any real issues when set a .020, just not within specs. (and Murphy's Law things can add up fast when things not within specs)
 
use the manufacturer spec on the air gap. Most are .010" I use a non-magnetic gauge courtesey of Briggs and Stratton or maybe Techumseh. Can't remember which.
 
sgkent said:
use the manufacturer spec on the air gap. Most are .010" I use a non-magnetic gauge courtesey of Briggs and Stratton or maybe Techumseh. Can't remember which.
Click to expand...
Take a micrometer and measure a business card to make sure it is close to .010”. I don’t think it is that crucial. Same as gap in spark plug. Most plugs I check when cleaning, the gap is too large until adjusted. Many spark plugs I check are not tightened properly either. Often the crush washer is not even seated.
 
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Tiger Small Engine said:
Take a micrometer and measure a business card to make sure it is close to .010”
Click to expand...
That's what happened. Thought is was under 0.010" but came in at a whopping 0.015". I set one last night at 0.006". Man that was some thin paper. Trying to make the biggest spark on these weak pusher coils of mine. And man she starts up buttery smooth now.
 
When it comes to magnetic induction, the air gap is critical for ignition coils. A small engine coil is just one of many examples of this technology.
 
inverse square law applies. The magnetic force at .015" is only twenty-five percent that of .0075" The magnetic field strengh is inversely proportional to the square of the distance from the source. At double the distance the field has to disburse over 4 times the area so it is only 1/4 the strength. That is why the measurement is important. Too close and it can rub or a small amount of dirt/grass can get ground up in it, and too far there is not strength. A brass or plastic shim of the manufacturers spec is what I use to check with. Also make sure that black sand particles, rust flakes etc., are not stuck on it.

Black sand (magnetite)

black-sand-phenomena.jpg
 
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