Caber rings for a Husqvarna 3120xp

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ArboristSite Lurker
Feb 6, 2019
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I recently rebuilt my 3120 that I purchased used. Piston had evidence of a four-corner partial seizure, with piston transfer on the cylinder, mostly on the exhaust side. After carefully removing the transfer with acid (yes, this works fine if you take it slow), I smoothed all the ports (some felt a bit rough even though the cylinder was OEM but it was an AB-sized cylinder with an AB-sized piston) and installed a new OEM piston with OEM rings (lazer-etched 'KO B8', I'm guessing Komarov rings). I was hesitant on using these rings as their gaps were quite large at 0.44mm and 0.45mm (for a 60mm bore). For reference, the gap should have been closer to 0.24mm if using the rule of thumb 0.1mm gap per 25mm bore (0.004"gap/1.0"bore).
Before installing the piston, I did a quick cylinder 'honing' with a pad of 3M scotch-brite on a cloth buffing wheel (slightly oversized to the bore) attached to a drill on low rpm, moving it up and down the cylinder about five times. The result was barely noticeable cross-hatching in the nikisil. After that, I thoroughly cleaned both cylinder and piston in hot water and soap. The cylinder was lightly-coated in 2T oil during assembly, as were all the bearings. Just documenting these steps so the typical naysayers here don't have much to discredit this top rebuild.

After only approximately 1.5 hours of varying work, I took off the exhaust to have a peek. I saw some very light scratches on the intake side of the cylinder. After taking off the cylinder, I found some very light scratches on the exhaust side as well. Piston skirts and rings appeared to be fine.
I took off the rings from the piston and refit them into the cylinder to recheck the end-gaps. After only 1.5 hrs of use, both rings gaps had grown to 0.635mm. This measurement is beyond the suggested replacement-time gap of 0.6mm = 0.25mm gap per 25mm bore. Close examination of both rings show that there is still the circumferential ridges on the outside of the rings, except nearest to the ends where it has more wear, but the ridges are still slightly evident there. There appears to be very slight rounding on the circumferential edges. The edges on the NIB OEM rings on my standby piston look far sharper. However, those standby rings have the same exact gap as the now slightly-used rings had when initially installed.
The cylinder looks great except for the very slight scratches above the inlet and exhaust ports.

The engine seemed to run very strong, but so much ring-wear is concerning.

For more reference, I'm using 100LL fuel at 25:1 ratio using Maxima K2 oil (full synthetic for high-heat engines).

A friend sold me an extra OEM cylinder and piston set a while ago, but they have more wear on them than what I am using now. But the rings look to be non OEM compared to what came in both of my new OEM pistons. They're stamped with 'SP' and they're finish appears like those of Caber F-cast rings -- shiny rather than black chromate like the OEMs. The rings had been sitting in the piston ring grooves for who-knows-how-long, and the top ring appears to have some transfer on it's bottom surface, so not too thrilled about using these, even though the outside face appears almost new, circumferential ridges hardly worn at all and very even in appearance. They're obviously made of a much harder cast material.

The big question is, where can I find real, official Caber rings, and should I use their softer cast rings, or go with the F-cast, as that is what seems most easily found. However, only the skeptical dealers who sell the chinesium saws have any 'Caber' stock. Anyone know of reputable dealers having Cabers in 60mm x 1.5mm(t) x 2.5mm(w)?
Thanks for your helpful and constructive comments.
Yeah, thanks, but I don't do ebay. Too many untruthful vendors. I'd far rather use a real vendor, someone like definitive dave, or randy, or... certainly not through fleabay. And like I stated before, someplace like Wagner's Chainsaws seems to only deal in chinesium saws, at least on his web site, so are those really Cabers he's peddling?... doubt it.
They’re Cabers. I’ve bought from him
But see, Kevin, EVERYTHING else Wagner sells is chinese. And there is a bunch of junk chinese 'cabers' out there, so....
The more people spend their money on cheap, flagrant, chinese copies of goods that are created in other countries by companies that invest heavily in design, fabrication and quality assurance of their products, the less quality and choice we will be able to find in products produced outside of china. I will not support anyone (like wagner or fenix supply) who pushes only stuff that all comes directly from china. We should all ask ourselves if saving a few extra pennies is worth throwing good (non-chinese) companies under the rug. Commie china is raking-in trillion$ from penny-foolish fools because of this WEF-created recession. Don't buy chinese!
Also, I wonder about the quality of goods made to be sold to chinese concerns, since the chinese concerns don't pay what non-chinese vendors will pay, and you can see this reflected in the price they charge us for those goods. Less than $4 for a Caber ring?! You gotta be kidding me.
Yup, I would agree, and that is what I tried. However, all the Husqvarna OEM rings that I have purchased for the 3120xp are too short (the end-gap is far too large) and they wear-out in a matter of hours of run-time. The OEM rings that are packaged with their pistons are obviously NOT the same as what comes in their assembled powerhead.
As stated in my original post, these OEM rings are marked 'KO B8' and from that I assume they are manufactured by Komarov S.R.O.
It's sad that Husqvarna believes that the guy rebuilding a saw can't trim the rings to the correct gap, so they specify a far too large gap to be too safe and super-soft ring material. I have three sets of new OEM rings and they all are the exact same with the same problems.
The cylinder mics-out to 59.998mm ID with nice, straight walls. The piston fits well with no rocking. I could be wrong, but there is nothing that I can detect that is amiss with the cylinder and piston fit, and the port openings have an acceptable chamfer and the edges are very smooth.
Sounds like you may have got a bad batch of rings or something.... they definitely should last longer than "hours" LOL!

I have ordered rings and other items from that same seller that huskihl mentioned with no counterfeit items showing up. There are other sellers on eBay if ya don't trust that particular seller... I'm sure plenty of other websites to get parts too.

If ya ain't satisfied with what ya get, send it back and move on. Sure it sucks, happens more often than it should, even I get hosed more and more every year it seems. But I damn well make sure to get a refund and leave negative comments. YMMV of course....
Yes chevboy, I have already been to their site, but they only have one set of rings. I was hoping for at least two sets. But for now I'll have to take what I can get. It appears that SawAgain does not get their stuff from china and don't pass off chinese junk as OEM and quality AM.
If you look at all the sellers on ebay, you'll discover that they all get their 'cabers' from china, all except SawAgain (maybe) and Wolf Creek. I am dead fast against purchasing anything that comes from china, or helping those resellers who are outlets for only junk direct from china. Just because 'Caber' is lazer-etched into the ring coming from china does not indicate that they are real Cabers. There are lots of bearings and rings and other products that are absolute forgeries that could pass as the real thing if one doesn't discriminate. Why help-out the chinese anyway when there are domestic sellers of the real mccoy? I always trust Wolf Creek, but they don't have these rings in stock at the moment.
I typically purchase the parts I may need far in advance of when I need them. The big problem with that recently (at least with these junk rings) is obviously I'm far past the point of returning the ill-fitting parts that don't work. That'll teach me.:confused:

Thanks all for the suggestions.

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