Piston circlip failure on Stihl 1127 series.

[fearofpavement]

Well, this is the very first mechanical issue I've had with aftermarket parts. I've built up a lot of saws using these Farmertec kits and to my knowledge the first failure.

I will post pics but I sold this Stihl 039 chainsaw to a guy that needed to cut up a 40" uprooted oak. He ran the saw about a day and then couldn't keep it running when it got hot. I told him I would make it right and gave him full value towards an MS460.

I had used this saw quite extensively so was puzzled why he had problems with it. (he owned a Stihl 029)

Anyway, he said he couldn't get the saw started but I fired it right up when he arrived but sent him home with the MS460 (and never heard another word).

This was a few months ago and I finally got around to opening the "low compression" saw up.

 

[fearofpavement]

Piston viewed through exhaust port looked great. Piston viewed through intake port looked great. Pulled the engine and found this.

 

[Stihlbillie]

Well that sucks ****

 

[fearofpavement]

Both circlips were present, both piston locating pins were present, bearings were fine and I determined that one of the "ears" had broken off the piston circlip. It apparently traveled from one side of the piston to the other and wreaked similar damage on both sides.

 

[Dave6390]

Well, that's a DooDoo sandwich with no bread! You think, or obviously know that the circlip didn't seat properly? What would cause that to just pop out and tear up the P & C?


Dave6390 in WI

 

[fearofpavement]

 

[fearofpavement]

The above pic shows the circlip with the ear present. The opposite side the clip was in place but the "ear" was missing. (more pics coming, give me a chance)

 

[Dave6390]

Is the Cylinder damaged to the point that it can't be cleaned up?


Dave6390 in WI

 

[fearofpavement]

 

[fearofpavement]

In this pic, you can see the ear not present on this side of piston but blurrily visible on the far side.

 

[fearofpavement]

I'll contact Huztl where I sourced this from and see what they'll do about it.
The cylinder is obviously damaged as well...

 

[wde_1978]

Circlip made of too hard material, got weakened when the "ear" got bent into shape, heat cycles and vibrations caused the ear to pop off due to material tension.

I see metal behaving like this on a regular basis, although in my case it is grey cast iron.

Was the circlip part of the P&C kit?
I think to remember to have read that some don't trust the AM kit circlips and opt to use OEM ones.

That is not fun, curious to hear what Huztl has to say about that.

 

[fearofpavement]

Yes, the circlip was part of the kit. The OEM clips are much smaller diameter. (smaller wire, not a smaller circle) so they don't fit well into the larger groove of the Farmertec pistons. I have used a lot of these kits but this has me concerned about the failure potential of other engines I have out there. As stated previously, this is the first "come back" I've had with these kits. I still have quite a few of these pistons in stock so will probably break that ear off after installation. I'm trying to decide what to do with a number of engines I have already assembled. Do I take them apart again? Is this an inevitable failure waiting to happen or was it an anomaly? Hmmm.

 

[wde_1978]

That really sucks, and not in a good way.
I wouldn't know nor dare comment on how to proceed with Your kit lot and assembled saws!

It might have been an anomaly, freak of manufacturing process - but then again whatever machine shapes those circlips makes hundreds of them in a blink of an eye.
I know than when I encounter one faulty cast at work, there are bound to be more within the production series thus additional caution is required.

Breaking the ears off sounds like a solid precaution measure, though I would be reluctant breaking them off while installed as steel that hard might chip and leave debris which again can cause engine failure.

I hope for you that this is a freak anomaly!

 

[CrufflerJJ]

. I still have quite a few of these pistons in stock so will probably break that ear off after installation.

If you break off the circlip ear, would you still be able to remove the circlip in the future should that be necessary?

 

[leeha]

I would never have used a circlip like that. Way to much ear there.
That ear would be flexing every time the piston stopped to change
direction. Either use a different style clip or cut most if not all of the
ear off.



Lee

 

[Definitive Dave]

Yes, the circlip was part of the kit. The OEM clips are much smaller diameter. (smaller wire, not a smaller circle) so they don't fit well into the larger groove of the Farmertec pistons. I have used a lot of these kits but this has me concerned about the failure potential of other engines I have out there. As stated previously, this is the first "come back" I've had with these kits. I still have quite a few of these pistons in stock so will probably break that ear off after installation. I'm trying to decide what to do with a number of engines I have already assembled. Do I take them apart again? Is this an inevitable failure waiting to happen or was it an anomaly? Hmmm.

I never realized the wire was a different diameter, I recommend using own clips, but if they don't fit I am not sure what to suggest.
I hate ears on a clip because they mean I can't use the circlip installer.
I was] of the opinion that caber rings and oem clips cured the tWho biggest deficiencies with most am kits
dave

 

[wde_1978]

Huh, I just took a look and discovered that I have two circlip styles sitting in a box as spares for my PS-6400/7900.
Both are supposed to be OEM.

Ear-less circlip from my NIB OEM PS-7900 P&C kit:


Single eared OEM replacement circlip the Croatian Dolmar/Makita dealer sent me:


Both circlip styles are made from 1mm/.038" thick wires and meant to secure a 12mm piston pin.

I believe I have seen pictures of circlips featuring two ears!?

Which one is the preferred style?

 

[CrufflerJJ]

I believe I have seen pictures of circlips featuring two ears!?

Some Meteor pistons come with two-ear circlips. I like this style, since it makes it easy (for me as a newbie) to gently install the circlip using needle-nosed pliers.

 

[fearofpavement]

I've never seen the two ear circlips in a chainsaw. I've seen ones with varying size single ears and no ears at all. The OEM ones in the 1127 series don't have ears.