Caber rings for 3400 Poulan

[kmcinms]

This topic may have been discussed in here before, if so, I haven't found the thread with detailed measurements yet. Who in here uses them in a Poulan 3400, or 3800(yes, larger dia. than 3400, same design) saw with factory chrome plated pistons? A good long while back I bought several Caber rings from Greece, never pulled them out to look at them, they were wrapped in heat shrink plastic wrap. FF to last week, getting a set of 3400 rings out of the package and notice they aren't blunt at the gap, they have the half tab design like Husky rings. It looks like I can file them blunt with plenty of meat to set end gap on the full round locator pin that Poulan used on these pistons. But that's only half the problem with using this set of Caber rings on a factory Poulan 3400 piston; read on:

After seeing that, I decided to mic the thickness of the rings for comparison to the factory rings. Sure enough, the Caber 1.5mm rings measure a perfect 1.5mm, but, they are .0035 thinner than all the factory rings(Husky and Poulan) that I checked. Factory rings mic out @ .062, aftermarket rings mic @ .0585 .
Axial ring clearance on factory pistons and rings is .002-.0025, which is perfect . Meaning the ring lands on the factory pistons are .0035 over optimum size for the aftermarket ring sets. Not good.
With this said, I have seen posts in Nik's Poulan thread with members scratching their heads when they can't get good compression when using Caber rings on factory pistons in these 3400s.
So after all that hot air, what rings are people in here using in their 3400 saws? If you used Caber rings, did they have the proper blunt ends, and proper axial height(thickness) to work on the Poulan piston? Pro Line advertises their rings with the same style ends as Husqvarna rings. that's not correct for the pistons in these saws.
EDIT: just got a message from Greece on their current stock of rings for the 3400; "Hello,

These rings have straight cut and their axial thickness is 1/16"."

 

[Highlander1959]

FYI, i just posted this on the other thread but the rings I just received appear to fit my 3400 piston and bore well. They're .061 by .079 and they fit the bore perfectly with essentially a zero gap. I have no idea if the material they're made of is suitable or not, but time will tell. I'd rather have a little softer ring that fits properly than use modified rings or rings that don't fit the bore properly and tear it up. These particular rings came from Little Red Barn, a vendor I've seen criticized heavily by some people here, but I'm going to try them out and see how they work for me. I've learned that people can be very biased when it comes to tools, trucks, and many other things. From what I've read, I think LRB's piston kits probably leave something to be desired since they're apparently not identical to OEM parts but we're running out of options for pistons and cylinders. All I know at this point is that these rings seem like a good fit for a factory piston so I'm going to try them.

 

[Lightning Performance]

You guys ever consider how thick the plating is on chromed rings?

I leave it at that.
Good Luck

 

[kmcinms]

FYI, i just posted this on the other thread but the rings I just received appear to fit my 3400 piston and bore well. They're .061 by .079 and they fit the bore perfectly with essentially a zero gap. I have no idea if the material they're made of is suitable or not, but time will tell. I'd rather have a little softer ring that fits properly than use modified rings or rings that don't fit the bore properly and tear it up. These particular rings came from Little Red Barn, a vendor I've seen criticized heavily by some people here, but I'm going to try them out and see how they work for me. I've learned that people can be very biased when it comes to tools, trucks, and many other things. From what I've read, I think LRB's piston kits probably leave something to be desired since they're apparently not identical to OEM parts but we're running out of options for pistons and cylinders. All I know at this point is that these rings seem like a good fit for a factory piston so I'm going to try them.

I don't know where they get the rings for their kits, never used any parts from them. As far as the cross section width goes, all I have to go by is my factory rings from a 3400, and from a 3800.
The cross section on both sets of rings varies all the way around the circumference because of how they wear inside the bore. The 3400 rings measure from .062 - .070. The 3800 rings are .060 - .074 around the circumference. The narrowest sections are 180 degrees from the locator pins in the pistons. Pretty sure that's why the compression on both these saws was in the 90psi and under range. not enough ring tension. hth

 

[kmcinms]

You guys ever consider how thick the plating is on chromed rings?

I leave it at that.
Good Luck

Does this saw use chrome plated rings? I've never heard mention of that on these rings that I recall. I'm not following you, what's your point, and why the snide "I leave it at that" remark? You either have info, or you're just throwing things out there.

 

[Highlander1959]

I don't know where they get the rings for their kits, never used any parts from them. As far as the cross section width goes, all I have to go by is my factory rings from a 3400, and from a 3800.
The cross section on both sets of rings varies all the way around the circumference because of how they wear inside the bore. The 3400 rings measure from .062 - .070. The 3800 rings are .060 - .074 around the circumference. The narrowest sections are 180 degrees from the locator pins in the pistons. Pretty sure that's why the compression on both these saws was in the 90psi and under range. not enough ring tension. hth

I just received and measured the LRB piston kit for the 3400. Aside from the fact that the piston isn't chromed, it appears to be identical in every dimension. The wrist pin is a tiny bit shorter but not enough to matter. The rings are factory standard size. I don't know where others were getting the idea that this kit had different sized grooves, rings, and wrist pin diameter. Maybe they were talking about a different kit. The ends of the rings are notched but I assume they took that into consideration ... all in all, I see no major problems with the kit and if it buys me another ten or fifteen years of life out of a saw that was on its way to saw heaven, I'll be happy. Time will tell.

 

[kmcinms]

I just received and measured the LRB piston kit for the 3400. Aside from the fact that the piston isn't chromed, it appears to be identical in every dimension. The wrist pin is a tiny bit shorter but not enough to matter. The rings are factory standard size. I don't know where others were getting the idea that this kit had different sized grooves, rings, and wrist pin diameter. Maybe they were talking about a different kit. The ends of the rings are notched but I assume they took that into consideration ... all in all, I see no major problems with the kit and if it buys me another ten or fifteen years of life out of a saw that was on its way to saw heaven, I'll be happy. Time will tell.

Is your factory piston done with? So far the two 3400s, and the 3800 pistons I have are in good shape, I need some 3800 rings. I have heard some tales about the lrb piston kit failures, but not from anyone I know in here.

 

[Jethro 2t sniffer]

I just received and measured the LRB piston kit for the 3400. Aside from the fact that the piston isn't chromed, it appears to be identical in every dimension. The wrist pin is a tiny bit shorter but not enough to matter. The rings are factory standard size. I don't know where others were getting the idea that this kit had different sized grooves, rings, and wrist pin diameter. Maybe they were talking about a different kit. The ends of the rings are notched but I assume they took that into consideration ... all in all, I see no major problems with the kit and if it buys me another ten or fifteen years of life out of a saw that was on its way to saw heaven, I'll be happy. Time will tell.

Do not use that LRB piston

 

[kmcinms]

Do not use that LRB piston

what happens when you do?

 

[Jethro 2t sniffer]

It lunches itself in about a minute with no coating on the piston

 

[Jethro 2t sniffer]

Post in thread 'Nik's Poulan Thread' https://www.arboristsite.com/threads/niks-poulan-thread.98495/post-6769588

 

[kmcinms]

Post in thread 'Nik's Poulan Thread' https://www.arboristsite.com/threads/niks-poulan-thread.98495/post-6769588

that didn't tell me anything. is it your saw that ate a piston? you have pics?

 

[Highlander1959]

It lunches itself in about a minute with no coating on the piston

Hummmm ... I have all sorts of small 2-stroke power equipment that uses bare aluminum alloy pistons and cylinders. I would certainly think that keeping the mixture set right, using a good oil, and mixing to the right ratio would be more critical but I can't see why the piston would just spontaneously fail because it isn't chromed. I don't know much about most of the members here but maybe the rings weren't gapped to the proper specs? Regardless, it seems I'll have to do a little experimenting and report back. I have a cylinder that's damaged (broken cooling fins) but measures well within spec. I'll probably try the new piston in that cylinder and see what happens. If an un-plated piston can survive in THAT cylinder, it should be able to survive pretty much anywhere.

 

[kmcinms]

Hummmm ... I have all sorts of small 2-stroke power equipment that uses bare aluminum alloy pistons and cylinders. I would certainly think that keeping the mixture set right, using a good oil, and mixing to the right ratio would be more critical but I can't see why the piston would just spontaneously fail because it isn't chromed. I don't know much about most of the members here but maybe the rings weren't gapped to the proper specs? Regardless, it seems I'll have to do a little experimenting and report back. I have a cylinder that's damaged (broken cooling fins) but measures well within spec. I'll probably try the new piston in that cylinder and see what happens. If an un-plated piston can survive in THAT cylinder, it should be able to survive pretty much anywhere.

you never answered my question earlier, so I'm guessing your factory piston is lunched. do you have pics of the p & c?

 

[Highlander1959]

Is your factory piston done with? So far the two 3400s, and the 3800 pistons I have are in good shape, I need some 3800 rings. I have heard some tales about the lrb piston kit failures, but not from anyone I know in here.

Well, it's not in pieces, but it's missing a lot of chrome. I'm not throwing it away just yet. If what I'm hearing is true and the un-plated piston from LRB is going to seize in five minutes (really?) then I might have to think about putting the OEM piston back in the saw with a new set of rings. I did manage to find a relatively nice cylinder so maybe the half-chromed piston will make compression and live a while longer in a better bore with new rings. The cylinder isn't horrible either, but about 1/3 of the top four cooling fins are sheared off so I figured I'd better find one that can cool itself properly. Again, only time will tell which, if any, of these approaches will work long term. We're definitely in uncharted territory with these obsolete saws.





Here's the bore. Not the greatest picture. Compression was 75 wet ....

 

[kmcinms]

That piston isn't terrible, but it's getting there. I'd run it before the bare piston. Measure the cross section of those rings, see how much wear there is @ 180 degrees from the alignment pins. That should tell you the story on your low compression numbers. Then Measure the ring land depth on the piston to see if the lrb rings will work in those lands. you do need space behind the rings, I can't recall what they recommend at the moment. You can get those dimensions off of the Wiseco site It should cross over to just about any small two stroke piston.

 

[Highlander1959]

That's the direction I was planning to go. If I put that other piston in a saw it'll be later when my options are more limited.

 

[Jethro 2t sniffer]

that didn't tell me anything. is it your saw that ate a piston? you have pics?

It told you everything. Jump on the poulan thread and ask for yourself. I'm only trying to help. You cannot run that piston. Steve will tell ya

 

[Highlander1959]

It told you everything. Jump on the poulan thread and ask for yourself. I'm only trying to help. You cannot run that piston. Steve will tell ya

I think we can all appreciate your words of warning about those pistons but the fact that one particular person has reported having a negative experience with one particular piston doesn't necessarily mean that everyone will have a similar experience. I can think of numerous potential causes for the premature piston failure Steve experienced, some of which have nothing to do with the piston itself. Yes, the lack of chrome plating could have been the cause - it will most certainly guarantee that the piston won't last as long as the plated OEM pistons. However, I find it rather difficult to believe that a company would be selling these pistons if they truly don't last 60 seconds when installed correctly in a properly tuned engine. I learned a long time ago that you can't believe everything you read or hear, especially on the internet. I'd recommend that anyone interested in these piston kits take your (and Steve's) words of caution under advisement and proceed to do their own due diligence before ruling out an option that may work just fine for them.

 

[Jethro 2t sniffer]

I think we can all appreciate your words of warning about those pistons but the fact that one particular person has reported having a negative experience with one particular piston doesn't necessarily mean that everyone will have a similar experience. I can think of numerous potential causes for the premature piston failure Steve experienced, some of which have nothing to do with the piston itself. Yes, the lack of chrome plating could have been the cause - it will most certainly guarantee that the piston won't last as long as the plated OEM pistons. However, I find it rather difficult to believe that a company would be selling these pistons if they truly don't last 60 seconds when installed correctly in a properly tuned engine. I learned a long time ago that you can't believe everything you read or hear, especially on the internet. I'd recommend that anyone interested in these piston kits take your (and Steve's) words of caution under advisement and proceed to do their own due diligence before ruling out an option that may work just fine for them.

I'm curious to see how it goes