What scored this?

[NCPT]

New to rebuilding and figuring out I should diagnosis the problem before tearing a saw down after a scored piston. Got this saw apart because scoring was harsh on exhaust side and intake side looked clean. Now that its tore down, there is scoring below the ring pins on the intake side. I took the impulse line off and blew in one end and gasket material came out, would a blocked impulse cause this type of scoring? Thanks

It's an 029 and I'm putting an 039 top end on it.

 

[NCPT]

 

[NCPT]

 

[NCPT]

Eff a clamshell saw lol

 

[shadco]

Looks pretty dry did you wash the crank and piston off?

.

 

[Wood Chopper]

Did this happen while you were running or is this saw new to you? Wish you could’ve pressure tested it before taking it apart looks like it went lean in a hurry. ?


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[NCPT]

Looks pretty dry did you wash the crank and piston off?

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Nope. Another thing I noticed was the AM fuel line was kinked the way it was routed. I have an OEM fuel line that came with the saw and it passes a pressure test. Blocked fuel line and blocked impulse line???

 

[NCPT]

Did this happen while you were running or is this saw new to you? Wish you could’ve pressure tested it before taking it apart looks like it went lean in a hurry. ?


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I got the saw to rebuild, new to this and realized I need to diagnose before tearing it down.

 

[Wood Chopper]

I’m sure someone will chime in that knows a lot more than me but neither one of those would cause the saw to seize like that. Bad impulse line would not let the carb work And a bad fuel line would just starve it for fuel


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[Wood Chopper]

Yep, new to this and realized I need to diagnose before tearing it down.

Yes I read your post again and I understand what you meant now I would go ahead and get everything cleaned up put everything back together with new piston new top end and all and then pressure test

I think you’ll be quite happy with the way it runs with an 039 top end and cross even makes a pop-up piston for it I believe you can buy them both together from HL supply. Actually I think you have to buy them together


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[NCPT]

I’m sure someone will chime in that knows a lot more than me but neither one of those would because he saw to seize like that. Black impulse line would not let the carb work And a bad fuel line would just starve it for fuel


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I'm thinking both conditions caused the problem.

 

[NCPT]

Yes I read your post again and I understand what you meant now I would go ahead and get everything cleaned up put everything back together with new piston new top end and all and then pressure test

I think you’ll be quite happy with the way it runs with an 039 top end and cross even makes a pop-up piston for it I believe you can buy them both together from HL supply. Actually I think you have to buy them together


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That's the top end I got for this saw. Thanks.

 

[Wood Chopper]

I'm thinking both conditions caused the problem.

I’m thinking more of an air leak if there was enough oil in the mix


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[Fruecrue]

Do you have a top end yet?

 

[NCPT]

Do you have a top end yet?

Yes, new parts came in today.

 

[qurotro]

New top end and new crank seal is needed. And what kind of sealant you're using to seal the clamshell?

 

[dall]

one word of advice reuse the oem screws that holds the motor together they are stronger than the aftermarket ones
i use motoseal on clamshells

 

[trooney]

I'd say there were two causes of the failure. Like @Wood Chopper said, a blocked impulse line would not let the saw run. I think you may have had a lean siezure along with some debris in the intake side. Just my thoughts. Search for piston failure analysis. DD put it on here. Its by Stihl and is a good guideline to go by. If you cant find it here, go figure, google it. It will lead you back to the document. Good luck with your build.

 

[treesmith]

I've seen similar on two saws that were started and put straight into wood before warm up, that time it was due to piston heating up before cylinder,

Not saying it is but it happens

 

[NCPT]

New top end and new crank seal is needed. And what kind of sealant you're using to seal the clamshell?