Piston & cylinder failure
- Thread starter Bfletch
- Start date
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RED-85-Z51
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Ive seen it on worn out high use engines like on backpack blowers and concrete saws where the skirt gets so thin it fails from piston rock/slap
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That should be the intake side. The bottom looks worn thin from concrete dust getting in by the air filter
Quite common actually, seen it many times on high hour engines in demo and chainsaws. Had a SD 116 in that the piston actually broke off just below the pin, worn thin as a sheet of paper.
Yes - K760. I'm not sure about the bearing, I'll have to look at it again.
Could be what the fellas above are saying, they prob have more experience than me. I’ve seen the skirts crack on race bikes with crazy hours just no saws yet. Makes sense though especially it being a cutoff saw. What I was getting at is if either big end rod bearing or wrist pin bearing is bad I’ve seen them smack the crank lobes and do this.
I have seen that happen multiple times on cut off saws with very high hours on them. The last one I worked on that had a broken skirt like yours the crank had movement because the bearings were shot. I have seen it on both Stihl and Husqvarna cut offs.
miller755
ArboristSite Operative
Brant,
I was going to ask you why you needed a crank when you bought the one from me, because I figured if your crank was trashed, the whole engine was likely worn. I was thinking that maybe you broke one of the crank ends off. These concrete saws live a terrible life, in the lot of 14 I bought some were only 2 yrs old and trashed. I do think I have some good cylinders if yours is too worn out, but I don't think I have any pistons that are good enough to sell, maybe a freebie, that will work, I do have a couple sets of rings, and crank seals, since you are digging in deep.
I was going to ask you why you needed a crank when you bought the one from me, because I figured if your crank was trashed, the whole engine was likely worn. I was thinking that maybe you broke one of the crank ends off. These concrete saws live a terrible life, in the lot of 14 I bought some were only 2 yrs old and trashed. I do think I have some good cylinders if yours is too worn out, but I don't think I have any pistons that are good enough to sell, maybe a freebie, that will work, I do have a couple sets of rings, and crank seals, since you are digging in deep.
Hey, thanks for the offer. I went in on this with the idea of getting a new piston and cylinder, which I did get from the dealer. I however, wasn't expecting this blown up piston, and the advice was to replace the bottom end too. The seals come in an entire gasket set (case, cylinder, intake, & exhaust) & bearings aren't that much. I just couldn't justify a new crank.
miller755
ArboristSite Operative
Good to hear.
banditt007
ArboristSite Operative
not sure if this covers that but its good info anyway http://texanalovestories.mathisacommonlanguage.com/PDFFiles_/(0005)Engine Failure Analysis Booklet.pdf
