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Is this piston & head salvagable?

#1

P

Psychlopath

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.

20180523_103938.jpg

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#2

Boobala

Boobala

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


#3

P

Psychlopath

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.


#4

EngineMan

EngineMan

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..!


#5

P

Psychlopath

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.


#6

reynoldston

reynoldston

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.


#7

EngineMan

EngineMan

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.


#8

Boudreaux In Eunice La.

Boudreaux In Eunice La.

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.....


#9

P

Psychlopath

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:

20180523_151536.jpg

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


#10

Boobala

Boobala

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.


#11

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Psychlopath said:
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:

View attachment 37931

Thanks for all the attention to the thread and the great info!
Click to expand...

The reason you got the same info on here as the shop is because a few of us own shops and do it for a living.....


#12

B

bertsmobile1

Not unheard of for an engine to run for years with a carb screw in there.
What I did notice or rather did not notice is an cross hatching in the bore and without that the rings will not seal so it is going to blow some smoke.
How much will depend upon just how worn the bore is.


#13

reynoldston

reynoldston

Boobala said:
the Intake valve does get a seal, none on the Exhaust understandable probably because of heat. Also Parts Manual shows only the Intake seal.
Click to expand...

The reason for the seal on the intake side is that there is vacuum under the valve and its there for oil burning control.


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