yt6800 misfire

[Jeff S]

I think I have a problem with my left side coil. It starts and runs fine for about 15 min then starts misfiring undee load.
I can pull the left side coil wire when its running and it stops misfiring.
I can also turn off the blades and it will misfire less often.
Things I have checked

-cleaned carb completely
-ohm test coils (both same)
-ohm test plug caps , one is 9k, other is 11k
-swapped plug caps from suspect coil
-remove coils, clean rust off surface and flywheel magnet
-reset airgap for coils
-.015 plug gap on suspect coil

Cleaning the rust off seemed to slightly help, but the problem persists.
I want to buy a coil but they are expensive! & if it doesnt fix it i wont be happy.

[Jeff S]

http://www.amazon.com/Replacement-Briggs-Stratton-395492-Ignition/dp/B003JW9CSC/ref=sr_1_27?s=automotive&ie=UTF8&qid=1405117537&sr=1-27&keywords=briggs+and+stratton+coil

I also can't help but to wonder if I could use a Briggs coil on this?

Hmmm...

$19 Briggs coil or
$140+ "Yamaha coil"  !!!

You could buy 7 Briggs coils instead of 1 Yamaha!!!
Any thoughts?

[cr250]

For $20 its worth a shot! I believe your on the right track with a coil issue.

[jim]

Do not understand one of your statements.
"I can pull the left side coil wire when its running and it stops misfiring. "
What wire are you pulling and does it stop misfiring or just does not get worse?

If the wire you are pulling is the kill wire it might be shorting to ground somewhere

[Jeff S]

I am pulling the actual left side coil wire right off the plug when its running.

Sequence of events

-Engine misfiring
-Pull left plug wire, engine stops misfiring
-Reinstall left plug wire, starts misfiring again

[jim]

I would check your valves to make sure they are opening and adjusted. Pulling off the plug wire on a motor with bad spark should not stop it from misfiring.  Good luck  strange problem

[Jeff S]

Problem fixed. It was left side coil.

I couldnt find any specs to get a Briggs coil that was even close so I could mod it.

1 other thing, the coil wire isnt shorter on this YS240TB coil. It is actually slightly longer.

[cr250]

So what coil did you go with? B&S or Yamaha

[Jeff S]

I went with the crazy expensive Yamaha.

If I wasnt working 6 days/week 60hrs+ I still think I couldve made a Briggs coil work.

Part number in case anybody else is looking for one.
 7LY-85640-01-00
This is from a 1990 Yamaha YS240TB Snowblower.