New OEM Piston chipping

[Jon1212]

Jon, was this ever resolved??

Was the cylinder out of round or tapered from top to bottom or both?

Did you use emory cloth or scotchbrite on the piston skirt to smooth it back out and try it again?


Did you file down the rough edges where the chips occurred?

I think the chips/flaking caused the scratches you see......

Poor manufacturing tolerances or too much silicon in the mix of the aluminum made it too brittle and then someone didn't deburr it well enough after final machining????



If I refer to my knowledge of pistons, I have much more background in Automotive pistons, and I have even seen some of those cause the same problems because of the same poor manufacturing/ deburring...

I have a friend that has all of the tooling required in making a determination as to what happened, working on it.

I do know that upon disassembly, by myself, I could see metallic flakes in the bottom of the case.

Hopefully @TermiteBuffet will have an answer fairly soon.

 

[Andyshine77]

Are you running a base gasket? I have a 5100 and the ears on the bottom of the cylinder were bottoming out just enough in the case, causing the cylinder to deform when you torqued the cylinder down. You couldn't tell the cylinder was bottoming out at all, the cylinder seemed to sit just fine in the case. However after inspecting the case you could clearly see where the cylinder ears were digging into the case.

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[TermiteBuffet]

Numbers and stuff.... checked the cylinder with a new ring from bottom to top about every .250 or so . Ring gap checked .013" consistently .. Cylinder checked 3 places 1.772"or 45.170mm at base area .. piston measurements 44.856 across skirt ,side to side 44.83 at top of piston ... I know the gap seems excessive , but this saw has very , very low hrs ... So.. ? ...The cylinder flanges were trimmed so they wouldn't bottom out ..Bearings are good checked and rechecked .. By all appearances the edges being sharp was letting some of the material chip off or flake off where it comes to a razor thin edge .. I could easily peel an apple with this piston , and I may do it just ..just because lol ...Advice appreciated , Good advice even more appreciated Thanks

 

[rynosawr]

Numbers and stuff.... checked the cylinder with a new ring from bottom to top about every .250 or so . Ring gap checked .013" consistently .. Cylinder checked 3 places 1.772"or 45.170mm at base area .. piston measurements 44.856 across skirt ,side to side 44.83 at top of piston ... I know the gap seems excessive , but this saw has very , very low hrs ... So.. ? ...The cylinder flanges were trimmed so they wouldn't bottom out ..Bearings are good checked and rechecked .. By all appearances the edges being sharp was letting some of the material chip off or flake off where it comes to a razor thin edge .. I could easily peel an apple with this piston , and I may do it just ..just because lol ...Advice appreciated , Good advice even more appreciated Thanks

For what my advice is worth.....

I think it was a Monday or a Friday piston at the Mahle factory.

I would buy another new one from a different source and lot number and check it for finish and sizing.

It may need to be warranted by the original retailer also if much different from the other replacement piston.

The excessive clearance near the crown or barrel shape of the piston is also likely causing the skirt to rock more than it would if the piston had a larger crown. This may be the reason for the excessive skirt wear along with little pieces of the piston skirt coming loose as well.

It is a cast piston and it may have been just a very bad sample. When I worked as an engine builder and parts guy, I saw a few cast dud pistons of good brands. Very few forged pistons with mistakes, but even that happened every once in awhile.

If you run that piston again, scotchbrite the skirt, and dremel all the edges to keep more from flaking off.

I would look for another piston and a warranty on that one if it were mine though.

 

[TermiteBuffet]

For what my advice is worth.....

I think it was a Monday or a Friday piston at the Mahle factory.

I would buy another new one from a different source and lot number and check it for finish and sizing.

It may need to be warranted by the original retailer also if much different from the other replacement piston.

The excessive clearance near the crown or barrel shape of the piston is also likely causing the skirt to rock more than it would if the piston had a larger crown. This may be the reason for the excessive skirt wear along with little pieces of the piston skirt coming loose as well.

If you run that piston again, scotchbrite the skirt, and dremel all the edges to keep more from flaking off.

I would look for another piston and a warranty on that one if it were mine though.

I got another brand new piston here oem that I can check tomorrow. ....

Pedal Tractor Loggin'

 

[wigglesworth]

Are you running a base gasket? I have a 5100 and the ears on the bottom of the cylinder were bottoming out just enough in the case, causing the cylinder to deform when you torqued the cylinder down. You couldn't tell the cylinder was bottoming out at all, the cylinder seemed to sit just fine in the case. However after inspecting the case you could clearly see where the cylinder ears were digging into the case.

Sent from my HTC One_M8 using Tapatalk

The 385 I did for the buildoff did the same thing....

 

[Jon1212]

For what my advice is worth.....

I think it was a Monday or a Friday piston at the Mahle factory.

I would buy another new one from a different source and lot number and check it for finish and sizing.

It may need to be warranted by the original retailer also if much different from the other replacement piston.

The excessive clearance near the crown or barrel shape of the piston is also likely causing the skirt to rock more than it would if the piston had a larger crown. This may be the reason for the excessive skirt wear along with little pieces of the piston skirt coming loose as well.

If you run that piston again, scotchbrite the skirt, and dremel all the edges to keep more from flaking off.

I would look for another piston and a warranty on that one if it were mine though.

Ryan,

I don't have a lot of confidence in purchasing another OEM piston as the price has increased to $80+ from $68. Also, shortly after(a month) I purchased the piston in question, I purchased a second OEM piston from a dealer here in Utah. Randy @TermiteBuffet has the second one for a second 5105 I picked up.
Both OEM pistons show the same crappy, non existent finishing.

 

[fordf150]

I got another brand new piston here oem that I can check tomorrow. ....

Pedal Tractor Loggin'

Get done comparing and measuring ship the old piston my way. I don't have any of the old part number pistons here to compare it with but I do have a few of the newest part number pistons here. Would like to see what the difference is between old and new numbers.

 

[TermiteBuffet]

But we still got the #3 combo pistons with the fried rice ....[emoji200]

Pedal Tractor Loggin'

 

[TermiteBuffet]

Get done comparing and measuring ship the old piston my way. I don't have any of the old part number pistons here to compare it with but I do have a few of the newest part number pistons here. Would like to see what the difference is between old and new numbers.

I can send you both pistons ...I may have a picture of the boxes if that will help. ...[emoji200]

Pedal Tractor Loggin'

 

[TermiteBuffet]

Both boxes

Pedal Tractor Loggin'

 

[fordf150]

Ryan,

I don't have a lot of confidence in purchasing another OEM piston as the price has increased to $80+ from $68. Also, shortly after(a month) I purchased the piston in question, I purchased a second OEM piston from a dealer here in Utah. Randy @TermiteBuffet has the second one for a second 5105 I picked up.
Both OEM pistons show the same crappy, non existent finishing.

Bad part is these pistons aren't from some china factory. Maybe piston quality is going downhill.... I have seen some really rough looking OEM stihl pistons over the last couple months too

Comparing your pics to the new piston I had here it looks like the finish is the same but would like to have piston in my hand

 

[rynosawr]

Ryan,

I don't have a lot of confidence in purchasing another OEM piston as the price has increased to $80+ from $68. Also, shortly after(a month) I purchased the piston in question, I purchased a second OEM piston from a dealer here in Utah. Randy @TermiteBuffet has the second one for a second 5105 I picked up.
Both OEM pistons show the same crappy, non existent finishing.

10-4.

I know what you mean.

If the finish is equally craptastic, I wonder what the sizing is like?

It may be the best option to buff and fluff one of those "extra-Flaky" factory pistons and reinstall.

 

[fordf150]

Both boxes

Pedal Tractor Loggin'

Second box looks like a Power Distributor relabeled box.

064 is the latest part number. Haven't seen any bulletins about pistons so not sure if the number change is just a number change or an update of some sort

 

[TermiteBuffet]

Second box looks like a Power Distributor relabeled box.

064 is the latest part number. Haven't seen any bulletins about pistons so not sure if the number change is just a number change or an update of some sort

So the top box might be yours ...maybe ? I don't know which piston I used for which saw...[emoji200]

Pedal Tractor Loggin'

 

[Jon1212]

But we still got the #3 combo pistons with the fried rice ....[emoji200]

Pedal Tractor Loggin'

 

[fordf150]

So the top box might be yours ...maybe ? I don't know which piston I used for which saw...[emoji200]

Pedal Tractor Loggin'

Bottom box would have been the one from me. For some reason power distributors put their label over the dolmar label

 

[TermiteBuffet]

Bottom box would have been the one from me. For some reason power distributors put their label over the dolmar label

Gotcha ...pm sent ...

Pedal Tractor Loggin'

 

[Justsaws]

Grind the piston(s), push the edge back enough to get a good stout bevel. Personally would not order any more OEM pistons without more information, specifically what is Dolmar's recommended clearance specs for that model saw.

Keep an eye on the squish, might want to check the crown displacement at full tilt, it is only going to get worse.

Who wants to get an Echo?
Yeah, you know who.

 

[Jon1212]

Grind the piston(s), push the edge back enough to get a good stout bevel. Personally would not order any more OEM pistons without more information, specifically what is Dolmar's recommended clearance specs for that model saw.

Keep an eye on the squish, might want to check the crown displacement at full tilt, it is only going to get worse.

Who wants to get an Echo?
Yeah, you know who.

Most of your post made sense, except the mention of Echo.