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Discussion Starter · #1 ·
Decided to change the head gasket on my decent running 1000 today, I was surprised to notice a hole in the middle of the piston... What is this about? Is this the design of the piston or has it failed?

This engine ran fine other than blowing hot air around the gasket.

I have changed a few gaskets on these engines but never seen a "hole in the piston".

What is the consensus? Normal? Not ok? Is this just a different type of piston someone used when they rebuild the engine?

ImageUploadedByTapatalk1448221520.362715.jpg ImageUploadedByTapatalk1448221533.348201.jpg
 

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I would say if it runs good leave it be, but not sure of the hole can't tell how deep it is from the pic.
 

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Looks like a dent from the manufacturer from the mold don't look the whole way through
 

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Discussion Starter · #6 ·
The hole does not go through, I used a small drill bit to get to the bottom by cutting through the carbon deposit, you can see the shiny spot in the bottom of the hole on the first pic.
 

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Discussion Starter · #7 ·
The oversize pistons generally had the hole in the center

s-l1600.jpg
Ah excellent, I figured it was manufacturing as the hole is perfectly round and perfectly centered.

What is the purpose of this?

Engine looks good other than one of the valve guides being a little worn, I have the part here and will have a go at changing that out.
 

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The hole looks to be for a center for turning it on the lathe when it was made at the factory.
 
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