Stihl 028 super rebuild went bad

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acarpenterdad

I like Husqvarna chainsaws...
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My saw that I just rebuilt last sept. Had the piston fail. A lot of you guys walked me through how to fix it at that time. Ive cut a couple of cords with it and it ran great. In hindsight, it did get harder to start about a month ago. The last time i used it, i set it down to gas it up and it wouldnt restart. After trying different things i put a compression tester on it. 30 psi. . I pulled the cylinder and the exhaust side off it has scuff marks and the piston is ground up on that side only. I certainly thought id get more use out of it than that. What do you think caused the failure?
 

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Heat from running lean or on straight gas usually causes this. Air leak somewhere, perhaps from the crankshaft seals is another possibility.
Its not lean, had plenty of power. No straight gas. I tested both vacuum and pressure after the rebuild.
 
Its not lean, had plenty of power. No straight gas. I tested both vacuum and pressure after the rebuild.

Na he means did you pressure & vac test post melt down and before you pulled the cylinder this time.
Add some photos of the cylinder- from the inside looking through the exhaust post if you can- some of those scores look pretty meaty, like it might have been eating carbon.
Diamond is just real old carbon........ and they are pretty damn hard.
 
Probably the same thing that caused a failure the first time and was not corrected. Don't make that mistake again. BTW wood doctor usually straight gas will have scuffs all around the piston, not just at the exhaust.
The first time was after my son used straight gas. The scoring then was predominately on the intake side but there was some all around.
 
Na he means did you pressure & vac test post melt down and before you pulled the cylinder this time.
Add some photos of the cylinder- from the inside looking through the exhaust post if you can- some of those scores look pretty meaty, like it might have been eating carbon.
Diamond is just real old carbon........ and they are pretty damn hard.
no, i didnt check pressure this time. I thought i had posted both pics initially but i see i didnt so heres the cylinder.
 

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My call would be lean- if not by mix ratio, then by excessive air entry. You might be best to list what you did with the rebuild, parts replaced and where those parts came from.
Tell us what the diagnosis was for the first meltdown and how it was corrected.
Full list of parts and their country of origin will narrow down some suspects.
 
Heres pics of the carb side, its pretty clean.
Na he means did you pressure & vac test post melt down and before you pulled the cylinder this time.
Add some photos of the cylinder- from the inside looking through the exhaust post if you can- some of those scores look pretty meaty, like it might have been eating carbon.
Diamond is just real old carbon........ and they are pretty damn hard.
Also, the muffler wasnt obstructed.
 

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Heres pics of the carb side, its pretty clean.

Also, the muffler wasnt obstructed.

I wasn't meaning the muffler as such- more stalactites and stalagmites of carbon building up in the port of the cylinder- popping off and entering the combustion chamber.
Can also happen with carbon build up in the top of the combustion chamber.
 
My call would be lean- if not by mix ratio, then by excessive air entry. You might be best to list what you did with the rebuild, parts replaced and where those parts came from.
Tell us what the diagnosis was for the first meltdown and how it was corrected.
Full list of parts and their country of origin will narrow down some suspects.
https://www.arboristsite.com/community/members/acarpenterdad.160885/This was my original post about the first rebuild. I did replace the piston with a meteor and cleaned up the original cylinder. I did too many other things to list!
 

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I wasn't meaning the muffler as such- more stalactites and stalagmites of carbon building up in the port of the cylinder- popping off and entering the combustion chamber.
Can also happen with carbon build up in the top of the combustion chamber.
It looked pretty clean to me
 
https://www.arboristsite.com/community/members/acarpenterdad.160885/This was my original post about the first rebuild. I did replace the piston with a meteor and cleaned up the original cylinder. I did too many other things to list!

Yeah, na. Im not reading through 11 pages to see what you did or did not do, be easier for you to narrow it down to a list of parts replaced and if they were OEM or AM.
If it had a heap of hours on it before you dropped a new top on it only- without any other expendable items being replaced- then something designed to keep air out might have failed since your new top end was fitted.
 
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