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Murray 425007x92a Spark Plug issue

#1

Nissannismoz

Nissannismoz

Hello, I finally got my mower up and running, but there's a catch.
I need to know if its possible to put the spark plug in too deep? If I put it in, almost all the way, the spark plug gets smacked, and it closes the gap on it.
As far as I can tell, this is the correct spark plug for this mower, it ran just fine until I took it out and put it back in. I only took it out to clean it from where it had a flooding issue - which is now resolved.
But could I have put the spark plug in too deep?
I put a new plug in, this time a E3 plug (the E3 3.20) because it says its compatible with the RC12YC plug. The plug that was in it was the same length and all, put it in, and bam, the gap gets closed on this new plug too!
So I put it in half way, and it runs like a dream - BUT I know this cant be safe or right. I'd almost think the plug is too long, and incorrect, BUT that's what the mower calls for!
A Murray part #5066 seems to translate over to a RC12YC plug.
This is a 17HP B&S I/C motor with OHV.

Please help! I'm scared to put this plug back in all the way for the fear of damaging the piston. But I also don't want to run it with the plug half in, either.
Thanks!


#2

D

Darryl G

The plugs you mention do appear to cross reference, but the question is whether or not that's the right part to begin with. Since the Murray manual doesn't cover the engine, we'll need to know exactly which engine you have. There should be a sticker on it that tells the model # etc.


#3

Nissannismoz

Nissannismoz

Darryl G said:
The plugs you mention do appear to cross reference, but the question is whether or not that's the right part to begin with. Since the Murray manual doesn't cover the engine, we'll need to know exactly which engine you have. There should be a sticker on it that tells the model # etc.
Click to expand...

Looks like it says model: 313707 type: 0126-E1


#4

D

Darryl G

Well, that's interesting. It appears that RC12YC is the right plug and that the E3 3.20 is a direct replacement for it. So the gasket is on the plug, the metal washer at the base of it? Your piston should not be hitting it the plug!

Your issue is beyond me at this point. I was pretty sure I was going to find that you had the wrong plug. Hopefully one of the top-notch mechanics who frequent here will have an explanation/solution.


#5

ILENGINE

ILENGINE

I suspect that something is stuck to the top of the piston in the area of the spark plug gap. Sometimes when you remove the plug or have has in cylinder issues things can break loose and cause issues.


#6

Russ2251

Russ2251

Find top dead center and measure depth to piston crown with a stick (wood or plastic)
into plug hole and compare to plug length/reach.


#7

Boobala

Boobala

Yeah this is a head scratcher, the ( RC12YC ) is what's called for ..PLUG CHART.PNG

I use this plug in my 17.5 HP & my 21 HP Briggs, the only time I've seen this issue, is the changing of internal parts,

Con rod, piston, head-gasket-(thinner or grooved for steel o-ring) , cylinder change (deck clearance shaved), or valve train components, ( including push-rods) changed, BUT I'm figuring NONE of THAT was done, a correct plug SHOULD have the proper clearance and NORMALLY, clears the piston & valves without a problem, I would think you would strip the threads if you over-tightened too much, unless the plug-hole had been stripped, and repaired with a Heli-coil, which IS possible, and that the thread-INSERT, was NOT installed properly, and it slipped into it's bore, from over-tightening (ie.) as you thread the plug in it sort of locks on to the Heli-coil then BOTH screw down into the head, I think you MAY have to remove the head, screw the plug in, and take a look-see. ..... :confused2:


#8

EngineMan

EngineMan

Did the washer (spark plug seal) come off when you took it out/cleaned it/replaced it...? if not try replacing it with a RJ12YC which is 9mm shorter and see...!


#9

B

bertsmobile1

Nissannismoz said:
Hello, I finally got my mower up and running, but there's a catch.
I need to know if its possible to put the spark plug in too deep? If I put it in, almost all the way, the spark plug gets smacked, and it closes the gap on it.
As far as I can tell, this is the correct spark plug for this mower, it ran just fine until I took it out and put it back in. I only took it out to clean it from where it had a flooding issue - which is now resolved.
But could I have put the spark plug in too deep?
I put a new plug in, this time a E3 plug (the E3 3.20) because it says its compatible with the RC12YC plug. The plug that was in it was the same length and all, put it in, and bam, the gap gets closed on this new plug too!
So I put it in half way, and it runs like a dream - BUT I know this cant be safe or right. I'd almost think the plug is too long, and incorrect, BUT that's what the mower calls for!
A Murray part #5066 seems to translate over to a RC12YC plug.
This is a 17HP B&S I/C motor with OHV.

Please help! I'm scared to put this plug back in all the way for the fear of damaging the piston. But I also don't want to run it with the plug half in, either.
Thanks!
Click to expand...

What have you done to the mower to "finally get it up & running "
Any engine work ?


#10

EngineMan

EngineMan

bertsmobile1 said:
What have you done to the mower to "finally get it up & running "
Any engine work ?
Click to expand...

Now that's a good question...!


#11

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Got me curious too........... Heli coil a good possibility on that being the issue ~!~!


#12

Nissannismoz

Nissannismoz

Hmm, all this has me worried! It runs like a champ, but all that was done was the carb was removed and replaced the float, the needle and cleaned the bowl out a bit because it was flooding excessively. The issue turned out to be the float was stuck.
Maybe the excessive gas was causing it to bend the tip? I'm scared to put the plug all the way back in, in worries it'll bend again (but this time, with damage.) It didn't look like anything actually came in contact with the plug, no metal on metal at least, but I'll take a picture of the old plug and see what you guys think. Maybe I'm overthinking it and the gas caused a sort of hydrolock and bent the tip on both spark plugs.
...if that's possible.
As far as I'm aware, this motor has never been taken apart, the person I had work on the carb said it looked like the carb had never been removed.
The flooding issue was pretty bad though. To a point the oil was contaminated with fuel so badly it looked as thin as water.
I have ran the mower for about 2 hours in it's current state, mainly just to see how its going to hold up with it's new repairs, and has done well, starts quick and easy, no smoke and oil looks/smells clean and clear.


#13

B

bertsmobile1

Fuel will not cause a plug electrode to bend
Only 3 possibilities
1) con rod is loose allowing piston to come closer to the end
2) debris entered the cylinder while the carb was off and that is hitting the electrode ( includes debris working loose )
3) A bent valve / detecthed valve seat is hitting the spark plug.
A head gasket is about $ 10
It takes about 3 hours ( including cleaning ) to replace one.
About 1/2 hour if you do not remove the carb or muffler and just wipe the big bits of dirt off.

OTOH it take about 3 times as long to pull the engine, and replace the con rod.
I know which I would rather do.
You can keep on faffing around trying this measuring that but it is only around 15 bolts to pull the head .
Rotate the engine to TDC on the firing stroke so you dont have to loosen the rockers then all you have to do is remove the rocker cover , the muffler, the manifold to head bolts ( 2 ) and pull the breather tube,
Undo the head bolts, give it a tap and you will know for sure.


#14

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Nissan.... Bert Is right on a valve seat may have come loose in the head..........

Did you get a new RC12YC new plug to put into it to make it run like a champagain ?? Or just halfway like you said earlier ???

Another thing, is a valve guide is in the wrong position and a valve rod is bent causing anther issue.....

Take the 4 valve cover bolts off first... Turn the engine by hand with the spark plug out and the plug wire WAY OUT the way.... Don't ask a friend of mine why.... That's a different story on a mower I had to redo almost all the way...It takes a pretty good eye to see if the rocker arms are opening and closing the way they should be....

If not take the push rods out 1 at a time and see if 1 is bent... Make sure 1 at a time, there is an aluminum one and a steel one......


If you need to take the head off take the 8 head bolts off in a criss cross pattern.... The carb intake are 2 bolts and 2 exhaust bolts should come off 1st....

Take the head off and see how the piston looks like IL Engine said something might be in there....

A buddy had a outboard engine in last week and the plug broke in the head and the piston was beat up bad to the point of no return and another piston was shattered and con rod in pieces... Crank was bad... so 7,000 bux later for a new power head he was running in the Gulf of Mexico again.......

Let us know Mon Ami ~!~!


#15

B

bertsmobile1

Boudreaux In Eunice La. said:
Nissan.... Bert Is right on a valve seat may have come loose in the head..........

Did you get a new RC12YC new plug to put into it to make it run like a champagain ?? Or just halfway like you said earlier ???

Another thing, is a valve guide is in the wrong position and a valve rod is bent causing anther issue.....

Take the 4 valve cover bolts off first... Turn the engine by hand with the spark plug out and the plug wire WAY OUT the way.... Don't ask a friend of mine why.... That's a different story on a mower I had to redo almost all the way...It takes a pretty good eye to see if the rocker arms are opening and closing the way they should be....

If not take the push rods out 1 at a time and see if 1 is bent... Make sure 1 at a time, there is an aluminum one and a steel one......


If you need to take the head off take the 8 head bolts off in a criss cross pattern.... The carb intake are 2 bolts and 2 exhaust bolts should come off 1st....

Take the head off and see how the piston looks like IL Engine said something might be in there....

A buddy had a outboard engine in last week and the plug broke in the head and the piston was beat up bad to the point of no return and another piston was shattered and con rod in pieces... Crank was bad... so 7,000 bux later for a new power head he was running in the Gulf of Mexico again.......

Let us know Mon Ami ~!~!
Click to expand...

And take the carb off at the manifold to head bolts cause then you dont have to touch any of the controls just hold it out of the way with a bit of old fence wire or a coat hanger.
This saves a lot of messing around working out what went where.
and I forgot, a new rocker gasket as well.
Put some axel grease on the head side of the rocker gasket so it strips off clean next time.

The longest and hardest part is getting rid of all of the Devils snot ( silicone ) that gets applied by 3rd rate mechanics all over the place like a 5 year old with a jar of peanut butter.


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