Ignition coil gap... a word of caution

I recently stripped down and cleaned a Makita EA6100P (Dolmar ps-6100). There was a lot of oily saw dust packed in around the ignition coil, so I removed the coil and cleaned out that area. When I reinstalled it, I used a business card to set the gap, which is what I've always done in the past.

When I got the saw back together it wouldn't start. I checked the plug, and it wasn't sparking. It was a new plug, so I figured that it wasn't getting power from the coil.

Out of curiosity I pulled out my dial caliper and checked the thickness of the business card I had used. It was 0.016" and felt a little thicker than a normal business card. I found one of the cheap doctor's appointment reminder cards in my wallet and that measured 0.01" thick. I set the gap again using the thinner business card.

The saw started on the first pull...

So my word of caution is, if you're going to gap the coil with a business card, use a cheap (thin) one, and not a "fancy" thicker type card. The 0.006" difference between the two was the difference between my saw running great and not running at all.

 

Thank you for the info

 

I used to use a twice folded piece of paper from a notepad when I worked in a repair shop. Worked great for me.

 

Ive always heard and used the business cards, good to know they vary in thickness. Maybe the folded notebook paper would be more reliable. Good info!

Sent from my SM-S536DL using Tapatalk

 

Makes sense. Normal paper is around 0.004", so folded in half gets you 0.008". I think most manufacturers recommend around 0.01".

I don't think "too close" matters as long as it's not rubbing.

 

I set mine with a folded sheet of paper too. I also side gap the spark plug. It makes a difference.
I just side gapped the plug in my 372 and it picked up a good bit of zip and needed a retune.
Getting that electrode out of the burn path makes a big difference at 10k+ rpm.

 

I always wanted to be as close as possible without any rub. Some are way more forgiving than others, but if you set them all 'tight', you'll probably get fire.

 

I remove the appropriate feeler gauge from the set and use it. If there is a range they list I go for the middle. Feeler gauges are cheap and accurate.

 

100%!!! Then you KNOW exactly what you're setting it at instead of assuming some piece of paper is a certain thickness.

The appropriate tool goes a long way sometime.

 

Same here. If I'm out in BFE and no feeler gauge on hand, then I'll get creative and use a matchbook cover or similar.

 

Excuse my ignorance but what is side gapping a spark plug?

 

Tell me more... What does it mean to "side gap" a spark plug, how do you to it, and what gap do you set?

 

My feeler gauges are flat and the gap I need to set between the coil and flywheel is curved. How do you set it with a feeler gauge? I'm all for precision.

 

I use brass shim stock to set my coil gap.
Consistent thickness and non magnetic.

 

I'm pretty sure feeler gauges are meant to bend.

I take the feeler gauge the long way over the trigger on the flywheel cause the gauge bends easier that way. Then move the coil to the correct position and tighten. Then rotate crank to remove feeler gauge.

 

Ah, yes, long way makes sense. I was thinking of poking one in from the top.

 

Just gotta look at it from a different angle.

 

Side gap is shortening the ground strap, so it is not directly over the tip of the electrode. This tends to make the spark a little more exposed and not hidden under the ground strap at the electrode tip.

 

Can also index the plug so the ground strap isn't in the way. Side gapping is probably easier since you don't need different thickness washers.

 

So it's still partially over the tip and not rebent so it's toward the side of the electrode?