126M02-6675-F2 Won't Run - Replaced Carb & Flywheel Key - Still No Go

[bertsmobile1]

Modern fuel is conductive at cylinder compression pressures
Modern fuels will leave an oily residue on the spark plug nose
Electrical resistance increases with pressure .
So it will spark beautifully in open air but in the engine spark will track down the side of the plug following the path of least resistance
This is why you hear that a good magneto will throw a 1/4" to 1/2" spark ( or better ) outside the engine yet the gap is only around 0.030".

 

[SamB]

One thing that I have learns in my many years of repairing mowers is never trust the spark plug.

I was recommended this plug for my Briggs engines by a pro mower guy. He says it is way more resistant to carbon fouling and misfiring. He has a gang of summer workers that are NTB and will over-choke an engine until it starts to sputter and sputter and foul a regular copper plug. I have had no starting issues but wonder if it's a worthwhile upgrade?

Amazon.com: Autolite XST458DP Xtreme Start Iridium Lawn & Garden Spark Plug : Patio, Lawn & Garden

Amazon.com: Autolite XST458DP Xtreme Start Iridium Lawn & Garden Spark Plug : Patio, Lawn & Garden

www.amazon.com

 

[ILENGINE]

@SamB The problem with the plug isn't direct fouling. The problem is the porcelain is not sealed and gas is conductive at combustion pressures. The gas soaks into the porcelain causing internal shorting of the components.

 

[bertsmobile1]

@SamB The problem with the plug isn't direct fouling. The problem is the porcelain is not sealed and gas is conductive at combustion pressures. The gas soaks into the porcelain causing internal shorting of the components.

This is the reason for those "bad out of the box" spark plugs you occasionally hear
Every spark plug is tested at least 8 times before it is put in the box so every one is good when shipped.

 

[SamB]

@SamB The problem with the plug isn't direct fouling. The problem is the porcelain is not sealed and gas is conductive at combustion pressures. The gas soaks into the porcelain causing internal shorting of the components.

Is this just another case of cost cutting,buyer be damned? Glazing the porcelain would add to the cost so why do it if the plug will last a season! As for me, I'm happy with my Briggs and Stratton branded spark plugs.

 

[ILENGINE]

Is this just another case of cost cutting,buyer be damned? Glazing the porcelain would add to the cost so why do it if the plug will last a season! As for me, I'm happy with my Briggs and Stratton branded spark plugs.

Part of it may be cost cutting, but it came about due to fuel injections engines. the different environment of fuel vaporization made the need for sealing the ceramic porcelain less necessary.

And I have replaced more Briggs branded plugs due to failure than any other plug that I have come across The year they came out with the engines that used the .020 gaps I was replacing plugs in customer mowers about once a week.

 

[bertsmobile1]

Is this just another case of cost cutting,buyer be damned? Glazing the porcelain would add to the cost so why do it if the plug will last a season! As for me, I'm happy with my Briggs and Stratton branded spark plugs.

Nothing what so ever to do with cost cutting.
All about badly written pollution laws and much more sensitive equiptment .
Pollution laws state 0.000% lead in exhaust gasses
The only glazes that will withstand engine conditions are lead based so they can no longer be used on spark plugs .
Now 30 years ago when the laws were written you could not measure lead in exhaust emission down to the 3rd decimal place
Now days we can do it down to the 6th decimal place
So when the laws were written the best we could do was 0.00%
I used to do metal analysis & health monitoring was part of the job
When microwaves came in some of the workers who never showed any lead pick up started to have lead in their urine
Th reason was they reheated old tea in their white porclean cups ( imported from Mexico ) and the glaze on the cups was lead based
so heating in a microwave liberated the lead .
For the fun of it we tested all of our own crockery and yes all of them infused lead into the tea , both the cups & the teapots
So from that day on nothing went into my microwave that was not in a glass container

 

[SamB]

Part of it may be cost cutting, but it came about due to fuel injections engines. the different environment of fuel vaporization made the need for sealing the ceramic porcelain less necessary.

And I have replaced more Briggs branded plugs due to failure than any other plug that I have come across The year they came out with the engines that used the .020 gaps I was replacing plugs in customer mowers about once a week.Y

Your favored plug for the 500cc briggs is what? A good spark plug eases the strain on everything on the engine,starter,battery,me. :-D

 

[ILENGINE]

Your favored plug for the 500cc briggs is what? A good spark plug eases the strain on everything on the engine,starter,battery,me. :-D

I try to avoid anything related to Champion. Have had to throw away complete cases due to immediate failures after installation. And The Briggs plugs are made by Champion. I prefer NGK, but they are not perfect either. My NGK failures have been less in 20 years of use than the Champion plugs I have had fail in one week.

I prefer the B2LM/BR2LM for the flat head engines and the BKR5E for the OHV engines in both Briggs and Kohler.

 

[bertsmobile1]

Unless specified by the customer they get NGK's because they are 50¢ cheaper & I charge the same price for all plugs.
NGK's also come in 10 packs & Champions or Bosch come in 4 packs or 10 x 4 packs
Same grades as Illengine unless there are signs of the engine needing a hotter plug.
OTOH
No 1 rule in engineering " if it ain't broke, don't fix it "
As such I would be lucky to change more than 20 plugs a year out of 300 or so jobs
I expect 50,000 to 100,000 miles out of my car plugs
I have plugs in engines that have not been changed since they were made and some of them are near 100 years old from the days of 2 piece plugs .