Is my problem the park Plug Gap? Mower manual says .040, engine manual says .030.

[chobbs1957]

I have a fixer upper YTH2348 Husqvarna mower (Model 960430035 00 - Serial 120806B002718). It is powered by a Briggs and Stratton Intek 23 HP engine (Model 445577 - Type 0755 E1 - Code 061117YG).

It sat at a friend's house for a couple of years with a rusted out deck, oil leak, and flat tires. He replaced with a Zero Turn Snapper and gave the Husqvarna to me.

The Husqvarna manual I downloaded reads that the spark plug gap is to be .040"; the B&S manual I downloaded says .030"; the old ones I replaced had a gap that when measured was .026". Go figure. Which is right? Could they be too close?


Both call for the Champion QC12YC, which I think is an "Electromagnetic Suppression (EMS)", whatever that means....

Anyhow, I am having trouble. I fixed the oil leak, just replaced the quick change plug with a standard nipple and plug. The thing cranked and ran like a sewing machine. I put another deck and tires on it from a donor machine I bought off Craig's List. However I have a problem with the machine shutting down after about 15 minutes of mowing.

I replaced the paper and the foam air filter, fuel filter, the fuel line from shut off valve to fuel filter to fuel pump, and the spark plugs. I took the machine and drove it around and mowed a little around neighbor's grape vines, doing fine, but, yes, it seems a little underpowered, even when cold.

Yesterday, while cutting in another yard, it resumed same patterns. Again, it also seems a little underpowered even when cold. I could delay it a little by pulling the choke partially out, but that helped only for a few seconds.

 

[natenkiki2004]

Shutting down like that sounds like a fuel delivery problem, starvation. Not a spark plug issue.

To touch on your spark plug issue, I had conflicting information in a rototiller. I find it's best to go straight to the B&S manual for proper information. The Craftsman manual had the wrong spark plug in my case, far too short, didn't extend into the combustion chamber. I don't think I've ever found wrong information in a B&S manual.

 

[mechanic mark]

http://www.briggsandstratton.com/us/en/support/manuals/results?NTT=445577-0755* 0.030 spark plug gap, make sure you have correct plugs page 9 in manual , try using high test gas with B&S fuel additive per instructions. I would also adjust valves per instructions, remove and clean blower housing, flywheel, heads, etc. using cheap paint brush, rags, etc. time consuming & patience. Change oil & filter, always use B&S OEM parts.

 

[SeniorCitizen]

Definitely check for rodent nest under the shroud that could be blocking air flow. A strong air flow ( subjective of course ) on both cylinders should be felt about where you see my hand in the picture

If all else is well, I've never found plug gap to be too critical on a BS engine. Also I can see no advantage of a gap wider than 0.025" or 0.030 if that's what the engine manufacturer recommends. Please don't attempt convincing me a wider gap makes a hotter spark. But I'm already convinced too wide a gap can cause a misfire.

 

[Grassbandit]

Shutting down like that sounds like a fuel delivery problem, starvation. Not a spark plug issue.

To touch on your spark plug issue, I had conflicting information in a rototiller. I find it's best to go straight to the B&S manual for proper information. The Craftsman manual had the wrong spark plug in my case, far too short, didn't extend into the combustion chamber. I don't think I've ever found wrong information in a B&S manual.

Clean gas cap, make sure its venting and of course give the carburetor a thorough cleaning.

 

[bertsmobile1]

And don't forget to clean the gas tank as well plus replace all fuel lines.

As for plugs, the wider the gap the latter the spark jumps so it retards the ignition a smiggon.
The smaller the gap the sooner the spark jumps so it advances the ignition just a smiggon.

Small gaps require less energy to jump so you could get a 12,000 V spark ( number from the either )
A wide gap requires more energy to jump so it might not jump till voltage has hit 35,000 V .
Too big and it won't jump at all, too small and it will just leak down the side of the electrode so no spark again.

To explain, the voltage you get from the coil is not constant, it rises from nothing peaks some where from 60,000 V to 30,000 V then falls back to zero again.
On a magneto, the faster it spins the higher the voltage which is why so many saw & trimmer engines are a bitch to start.

 

[chobbs1957]

I left the machine with a repairman. He suspects coil. My mind has been spinning.

One other thing could be a deck pulley or mandrel being bad, putting an extra load on the motor when running. This deck came off an '04 model donor machine that had been sitting long enough to have seen at least a couple of birthdays from the same spot. When cool and engaged, machine does seem a little under powered, and I don't really think the engine is that far gone.

 

[ILENGINE]

I think the plug confusion is due to Husqvarna using both Kohler with uses .040 plug gap and briggs which is .030 gap.

 

[chobbs1957]

Repairman says no compression on right hand cylinder, can't touch top of piston with long screwdriver, says its a broken pushrod. No wonder I was low on power. This is bad.

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