Is this piston & head salvagable?

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Psychlopath

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• May 23, 2018 / Is this piston & head salvagable?

• #1

Today, I pulled the head off to replace the gasket and found some FOD.

It's clearly ingested something nasty, but was running and starting just fine before the tear down and I didn't see any cylinder wall damage with the piston at the bottom of it's travel.

I'm inclined to put it back together and keep on using it 'till it croaks. Maybe try to source a replacement in the mean time.

Since the damage is already done and it was running well before removing the head, is there any reason not to play dumb and just keep on keep'n on?

I don't think it matters, but this engine is a 31p777.

 

Boobala

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• May 23, 2018 / Is this piston & head salvagable?

• #2

In the pic with the spark-plug in the chamber, it looks like one of the valve guide's is popping out .......

 

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Psychlopath

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• May 23, 2018 / Is this piston & head salvagable?

• #3

I saw that and put a pin punch on it and it didn't budge, so I'm guessing that's where it's supposed to be. Looking inside of it, I can't see a gap or void to indicate that it's migrating, but I could be wrong.

With the condition of the chamber in the head, I'm not sure that it's worth worrying about either way.

 

EngineMan

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• May 23, 2018 / Is this piston & head salvagable?

• #4

Boobala said:

In the pic with the spark-plug in the chamber, it looks like one of the valve guide's is popping out .......

Click to expand...

The valve guide is out should be like the other one, whats been inside to make that damage..? and yes it can be repaired....if you what to go that way..!

 

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Psychlopath

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• May 23, 2018 / Is this piston & head salvagable?

• #5

EngineMan said:

The valve guide is out... whats been inside to make that damage..?

Click to expand...

Thanks, I'll look into that valve guide when I get back to it.

I looked a little further into things and sure enough, one of the screws in the carb butter fly is missing. That's what the engine ate.

Maybe that's why the engine was priced so well...

I removed the other screw and put thread locker on it. I thought these things were supposed to be staked to prevent this.

 

reynoldston

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• May 23, 2018 / Is this piston & head salvagable?

• #6

Sorry to disagree, the valve guides are made that way and are normal. I have some heads in my shop and all the guides are like that in them, its the intake side. As far as the damage on the piston and heads I have seen that many times and as long as it isn't useing oil you will get many years runing out of it so don't worry about it.

 

EngineMan

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• May 23, 2018 / Is this piston & head salvagable?

• #7

If the valve guides should be like that, then I have make a mistake, and yes it will run again just clean it up a little.

 

Boudreaux In Eunice La.

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• May 23, 2018 / Is this piston & head salvagable?

• #8

Yes the intake valve is supposed to be like that.....

I was gonna say to check your choke and throttle for a missing screw...... BLUE loctite is what I use.....

 

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Psychlopath

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• May 23, 2018 / Is this piston & head salvagable?

• #9

reynoldston said:

Sorry to disagree...as long as it isn't useing oil you will get many years runing out of it so don't worry about it.

Click to expand...

Thanks for that! I asked at the local mower shop, after I lost my exhaust gaskets and needed to replace and they confirmed what you said about the guide.
They also suggested that it's OK to run as it, but I may want to use a roloc disc and knock the high spots smoothish. Funny that the unexpected trip to the mower shop turned up the same info as this thread!

The mower was using oil, but I firmly believe it is because of the blown head gasket, so I'll see what happens after I wait for the muffler bolts that I broke to show up.

Here's a picture of the offender:



Thanks for all the attention to the thread and the great info!

 

Boobala

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• May 23, 2018 / Is this piston & head salvagable?

• #10

Just checked the Eng. Manual ( # 276781 ) Pages 94-99, The guides in the (97xxxx & 99xxxx series) have guides installed = 1/8 " above the bore, NO mention of other models needing a specific measurement, very vague, but the Intake valve does get a seal, none on the Exhaust understandable probably because of heat. Also Parts Manual shows only the Intake seal.