Meteor 066 cylinder kit - diagnose this scoring please

[Definitive Dave]

Cliff's Notes for the TLR crowd : light markings, slight ring scratching, what happened?

Details for the enlightened: About 3 weeks ago a customer bought a pair of Meteor MS660 / 066 cylinder kits from me and took his pair of older 064AV saws to his Stihl dealer for overhaul to use with his new 66' dbl end Cannon bar and chainsaw-mill. According to the dealer who talked to me (and has ordered more Meteor kits for his shop from me since then). One saw needed a coil and a good cleaning and the other had a slight leak at the cylinder gasket. The first saw took to the cylinder swap like a champ and ran well and tached properly from the get go. The second saw he said the piston felt tight in the bore on the new kit , but since he was still able to spin it in the cylinder he went ahead and reassembled the saw. During the initial tuning he said the saw acted funny and ran rough, so he shut it down after taching to 13, 000RPM and checked the piston through the exhaust and found the beginning of markings already within a minute or two of run time out of the wood.
I have seen some scored P/C in the past (maybe 100s by this point), but this seems odd. He said the circlips were installed properly and he used new OEM piston bearings. I sent a new kit out ASAP and Meteor immediately said they would send me an extra kit for free in this weeks order. New kit is installed and customer happy. The dealer told the customer subsequently that he spent a couple of hours working the top of the crankcase on a marble slab to get it true before installing the second new jug. I bought the two 064 p/c from the original customer and one of the jug shows similar marks on the piston, they are purely optical, nothing you can feel at all and on the OEM ringset there are no marks or scratches. On the Caber rings from the Meteor piston there are distinct tiny scratches. The original cylinders are both perfect no marks even. This cylinder has marks like the piston but again nothing you can feel.
To me it doesn't look like bad gas or traditional lean condition or piss revving and no sign of carbon on any ports. I am very curious as to what this might be. Tech said he thought bad plating on cylinder of new cylinder but that doesn't sit right in my head. Not looking to blame anybody, just gain a better understanding.

Yeah pics.
DDave

 

[lone wolf]

Cold seize, too tight? Measure it you said this all happened very fast before the saw even got hot am I correct?

 

[jughead500]

Just my opinion dave but i would say it was the rings and port bevel.are the rings sharp? Or beveled?
Ran into it on my buddy steves 036.5 minutes run time and it started doing the same thing.cleaned the cylinder and installed new beveled cabers and its just fine now.
Although the position of the scoring points toward an air leak to.either base gasket,seal on that side or even the decomp if it was used.

 

[Definitive Dave]

Pretty sure this kit comes with the F-cast Cabers, I know some builders prefer one over the other type, but they are new Cabers included with all Meteor kits.
The Cold Seize thing does seem like a possibility, despite common sense it is pretty common practice to wind that bad boy up as soon as it starts
The dealer didn't seem like an idiot and has done a ton of saws over the years, but that certainly crossed my mind. From what I think I know (always dangerous) cold seizing from dissimilar heating usually indicates with lines of scoring at the outer corners of the intake and exhaust ports like 4 vertical lines.
I will put the mic on it after I get back from replacing a mailbox I utterly crushed while plowing this year
The fact that he worked on the base gasket area for 2 hours between kits makes me a little suspicious in that area as well
DDave

 

[Moparmyway]

Mic the bore to eliminate one possibility. Move on from there, but at least you will know if the bore was or wasnt part of the equation

 

[nmurph]

Lean/air leak.

Why was the dealer monkeying with the base?

It looks like the cylinder has been honed?

 

[jughead500]

The rings i had in that 036 were the f cast with a meteor piston.should have stated that.
But as you and neal stated i'd say lean condition from the base gasket.

 

[pioneerguy600]

Check that port bevel closely on that cylinder, the scoring is mostly contained to the area of the piston that crosses over the exhaust port. I think there is a rough edge on the exhaust port, its common on all AM kits I have seen thus far.

 

[spindrift7mm]

Am I the only one that press/vac tests new builds ? Sure don't like the look of the port edges and I'd expect things to look oilier not dry ! Too many questions but if it was tight when I assembled it I'd damn sure measure it before going any further so I call assembly error. Air leak, port edges, dry assembly or tight bore should have been caught. Tight bore doesn't make a saw "run funny". Ken

 

[Mastermind]

Looks like either a rough bevel on that part of the exhaust......or an out of round jug. I've seen both in AM jugs.

 

[angelo c]

Looks like either a rough bevel on that part of the exhaust......or an out of round jug. I've seen both in AM jugs.

Randy,
you've played with far more Jugs then most...is it me or do all the ports and transfer edges look rough on that jug ?
I just looked at an OEM 066 jug and they are far more uniform.

I have installed Meteor slugs but not too many Meteor jugs to compare with.

 

[Mastermind]

Randy,
you've played with far more Jugs then most...is it me or do all the ports and transfer edges look rough on that jug ?
I just looked at an OEM 066 jug and they are far more uniform.

I have installed Meteor slugs but not too many Meteor jugs to compare with.

The Meteor kits, like most other am kits are all over the place when it comes to beveling, shape, and edge finish. That said, they normally have great plating, and we know they come with a damn good piston, and rings. That alone sets their kits a little above the competition.

The bevels look pretty good to me.......but like every other 066 AM top I've seen (except the standard bore Mako kit) the top of the exhaust port is far too square.

If the floor of that port is also that "flat", and it has a less than stellar bevel that could be what ate the piston. The floor of the exhaust is the hardest place in the jug to be 100% sure you have a nice bevel........you just can't really see it.

 

[angelo c]

The Meteor kits, like most other am kits are all over the place when it comes to beveling, shape, and edge finish. That said, they normally have great plating, and we know they come with a damn good piston, and rings. That alone sets their kits a little above the competition.

The bevels look pretty good to me.......but like every other 066 AM top I've seen (except the standard bore Mako kit) the top of the exhaust port is far too square.

If the floor of that port is also that "flat", and it has a less than stellar bevel that could be what ate the piston. The floor of the exhaust is the hardest place in the jug to be 100% sure you have a nice bevel........you just can't really see it.

thanks Randy,
I need more learnin on what to be lookin fer.

 

[Definitive Dave]

tossed the micrometer in the jug and piston and am a little surprised, I really expected the measurements to be dead on balls even all the way around especially the piston which is labeled as being a specific size

Piston measurements with harbor freight micrometer zeroed - 53.96 (as labeled), 54.01, 54.16, 53.95
Cylinder as above - 53.58, 53.87, 53.78, 53.82, 53.84, 53.79

so that makes it seem like the bore is smaller than the piston, but the piston will slide in to the cylinder - huh??

 

[Mastermind]

Have you got a bore mic?

 

[Definitive Dave]

nope, looks like I need another tool, hang on while I notify my wife and see if she kills me
looking at them on Amazon that looks like a specific tool for the job and one I should invest in. Any recommendations in the semi-serious hobbiest budget ($100 ish or less) ?

After seeing this one, it finally is sinking in why some guys insist on an OEM cylinder even with a Meteor piston and Caber rings. I have used/sold upwards of 100 Meteor cylinders and this is the first one that has had an issue like this, I was ready to blame the installer without really wanting to, but I can see it might be a product issue.

thanks for the great responses so far, another day of learning for me
DDave

 

[Mastermind]

I've got a set of snap gauges Dave. You put the gauge in the jug, lock it, remove, then measure with a caliper or mic.

http://www.amazon.com/Anytime-Tools-16-PRECISION-TELESCOPIC/dp/B000I8NDAS

 

[RedneckChainsawRepair]

I'm still wondering why they would spend 2 hrs on the base gasket?

 

[Woody912]

Lean/air leak.

Why was the dealer monkeying with the base?

It looks like the cylinder has been honed?

wondered the same thing, could have honed the plating off the cylinger?

 

[Definitive Dave]

I've got a set of snap gauges Dave. You put the gauge in the jug, lock it, remove, then measure with a caliper or mic.

http://www.amazon.com/Anytime-Tools-16-PRECISION-TELESCOPIC/dp/B000I8NDAS

added to cart!!
thanks

Yeah it seemed weird that he charged the guy an extra 2 hours to smooth the top of the crankcase before mounting the second cylinder, customer said he was leveling it with sandpaper on a marble slab.
All I ever had to do was use a razor to shave any gasket sticking out and give it the red goo. I wasn't there so I can't say.