McCulloch Chain Saws

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cpr

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SP125 came today. Looks very clean, bore and piston look good, but compression is only 95psi. Not complaining, just trying to figure it out.

1. Could the piston be hitting the schrader valve on my tester at TDC and not giving a true reading?

2. Decomp replaced with a bolt. Leak source?

3. Popsicle stick bore check seems to indicate stock bore and it is an unpainted, unnumbered block which I would guess is a replacement and would not have been bored. But if it indeed had been and reassembled with the wrong piston... I hope this isn't the case. This new job doesn't give me time to be tearing into a saw at that level.

Anyway, what do you guys think? I don't want to start it until I figure this out.
 
stinkbait

stinkbait

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SP125 came today. Looks very clean, bore and piston look good, but compression is only 95psi. Not complaining, just trying to figure it out.

1. Could the piston be hitting the schrader valve on my tester at TDC and not giving a true reading?

2. Decomp replaced with a bolt. Leak source?

3. Popsicle stick bore check seems to indicate stock bore and it is an unpainted, unnumbered block which I would guess is a replacement and would not have been bored. But if it indeed had been and reassembled with the wrong piston... I hope this isn't the case. This new job doesn't give me time to be tearing into a saw at that level.

Anyway, what do you guys think? I don't want to start it until I figure this out.

Something is not right with the decomp or your pessure tester. My 125 has the original cylinder and it is unpainted, so that doesn't mean anything.
 
leeha

leeha

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SP125 came today. Looks very clean, bore and piston look good, but compression is only 95psi. Not complaining, just trying to figure it out.

1. Could the piston be hitting the schrader valve on my tester at TDC and not giving a true reading?

2. Decomp replaced with a bolt. Leak source?

3. Popsicle stick bore check seems to indicate stock bore and it is an unpainted, unnumbered block which I would guess is a replacement and would not have been bored. But if it indeed had been and reassembled with the wrong piston... I hope this isn't the case. This new job doesn't give me time to be tearing into a saw at that level.

Anyway, what do you guys think? I don't want to start it until I figure this out.


How doe's the piston, cylinder look through the exhaust port.
I have seen many sp125's with unpainted blocks. It could very
well be original. The rings could be stuck in the piston grooves,
or just plain ole wore out.
I would say you will most likely be taking it appart.


Lee
 

cpr

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Pics...

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cpr

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Thanks Brian, how DO you do that?

Yeah that's the way it was listed alright.

I checked around a little more. Piston has a slight dent on the crown over between ports. I've seen much worse on here, I don't think that's the problem. The piston will rock quite a bit on the pin when you roll it slowly through compression. No satisfying little chuff when it breaks over tdc. Not sure the piston should move that much on the pin center line when I poke it with a popsicle stick through the plug hole.

Anyway, I'm done looking at it. I'm not going within a foot of it until I hear back from the seller. I'm keeping it, but it's not worth what I paid like this.

Guess I'll just be quiet about it for now until this is over...
 

cpr

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BTW, I believe I was wrong about the rings. They appear to be pinned and move freely within their limits, so that's not it, nor is it the plugged decomp. It's leaking past the rings.

Now I'll shut up. :mad-tongue:
 

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