Busted a ring this morning ??

[av8or3]

Engine has about 15 minutes since OEM refurb cyl and Meteor piston. Pics show break right in the middle of the exhaust port with corresponding damage to the cyl at that location. There are zero marks on piston or cyl anywhere else. Anybody got any ideas? Where did I go wrong? Thanks in advance. Jim

 

[dall]

what saw ? found this same problem in a 661 the piston was labeled wrong with the arrow
meteor piston

 

[dall]

could also be the port wasnt beveled enough

 

[hotshot]

What clearance did you your file your two Caber rings’ end gap to?

If you didn’t check, that’s likely your problem...

 

[av8or3]

No I didn’t check. Seems I’m learning something else the hard way. I know how it’s done but about where in the cyl do you measure and where do I find the spec for the 026? Nothing about it in the service manual that I have.

 

[Fruecrue]

Doubt it was ring end gap, check the other for *s-words and gigs.
Push it into the bore square (use piston) and measure with a feeler gauge.
Look at the factory ends of the broken ring, if they touched and pushed each other, there may be evidence of that.
Is it possible it was broken on assembly and lasted a few minutes before hanging in the port?
Did you inspect the ring for defects before or after? Still possible you could find a void in the metal if there was one.

 

[av8or3]

It for sure wasn’t broken on assembly, once installed, I watched it for several ups/dns thru the exhaust port before installing the muffler. It broke right in the center of the exhaust port. I think I would have seen it. I will measure ring end gap on the next one, and look for the spec, before final assembly. I’ve taken a stone to the damage on the exhaust port, both top and bottom. I finished with 1000 grit and checked for bulges at the spot as well using a bright light and a straight edge. It is flat, what’s left is a small divot in the center of both the top and bottom walls of the exhaust port that probably will leak something, maybe not. I’ll have to try it to see . Waiting for parts.

 

[hotshot]

I will measure ring end gap on the next one, and look for the spec, before final assembly.

It needs 0.008” minimum gap on that 026 with a 44mm bore. Push it in about a quarter inch & be sure that where the ends meet is over a solid part of the cylinder (not over a port).

I’ve had two pair of Cabers in the last month that were too tight, normally they’re good to go.

 

[av8or3]

Here’s another pic. It’s the area of the break in the ring that broke. I believe that there is a small missing piece that would be between these two. Hard to photograph but if you look closely you can see that there is serious wear to the EDGES of the ring in the area of the exhaust port. The edges have started to “round off” in the area of the exhaust port. How could that be interpreted?

 

[Fruecrue]

It needs 0.008” minimum gap on that 026 with a 44mm bore. Push it in about a quarter inch & be sure that where the ends meet is over a solid part of the cylinder (not over a port).

I’ve had two pair of Cabers in the last month that were too tight, normally they’re good to go.

View attachment 184111 Here’s another pic. It’s the area of the break in the ring that broke. I believe that there is a small missing piece that would be between these two. Hard to photograph but if you look closely you can see that there is serious wear to the EDGES of the ring in the area of the exhaust port. The edges have started to “round off” in the area of the exhaust port. How could that be interpreted?

I said previously that I doubt it was a ring end gap issue.
Maybe I was wrong.
If this pic shows the ring laid out like it was from the factory, one end is certainly damaged (on the left).

 

[av8or3]

There is another small part that I recovered with the ring end on it. It does look to me that it’s possible the ends were touching. They are very shiny as if they were rubbing. I don’t have another set to compare, but it can’t be a bad idea to at least check the gaps. I pressure test every saw I begin work on to get an idea of what lays ahead, now I’ll check every ring gap on new pistons as well. Do you think it would be necessary to check the rings on an OEM piston? I’ve still got one of those boxed up. The thought of stretching them to get them off and then again when putting them back on gives me the willies.

 

[Nutball]

The only Meteor cylinder I've seen (036) already had a 65% wide exhaust port and was pretty square. I gave it a really slight curve in the middle and good gradual chamfer just in case. That was the last cylinder I was sent from someone who said they liked my port work and kept sending cylinders. I don't know if he thought I was getting lazy since the meteor cylinder needed very little work. Plus I was starting to get more conservative with experience, but did my best polishing job on that one hoping to compensate the lack of grinding.

 

[Stump Shot]

View attachment 184111 Here’s another pic. It’s the area of the break in the ring that broke. I believe that there is a small missing piece that would be between these two. Hard to photograph but if you look closely you can see that there is serious wear to the EDGES of the ring in the area of the exhaust port. The edges have started to “round off” in the area of the exhaust port. How could that be interpreted?

Was having a hard time coming back into the groove when closing. Question is why? Check for too flat of a roof, too wide of a port, no bevel on the edge of the port or end gap too tight not allowing it to come back in, are a few things that I can think of to check for.

 

[Al Smith]

You could play Sherlock Holmes which is only speculation after the fact .I've had good luck with Caber and Meteor myself .Buff it out,new ring ,might be just fine .It doesn't take much ingested trash to snag a ring .Some times it makes it through the transfers and gets spit out the exhaust .Some times the poor old saw chokes on it .It's kind of like a fly in your beer can .Not to be confused with a bumble bee in same .Not good .

 

[Redfin]

Also check the thickness of the rings against the groove in the piston. Ive heard of thinner rings than the land shipped. Not just with Meteor.

 

[av8or3]

Thanks everyone, I appreciate you all. I’ll come back after I’ve successfully repaired the saw. Who said 2-strokes were simple? LOL

 

[Al Smith]

A lot can happen with a piston traveling that fast in very short period of time .

 

[redline4]

@av8or3 what do you mean by stretching the rings?

I put on hundreds of them a year. I always roll them on. I made a quick vid to demonstrate.

That way has never failed me or broken a ring.

I remove them the same way, just reverse motion.

 

[old guy]

I put a Hyway pop up piston in a 350 Husky today, couldn't get a .004 feeler in the ring gap, filed it open to .008.

 

[RI Chevy]

Maybe the ring was put in upside down causing it to expand and snap? Just thinking outloud. Glad it didnt do to much damage.
Cool trick there Ed.