If only one is mark you may have one new and one used. Now check the depth of each. Does the marked one have the .50 end gap and unmarked .58 or the other way around. Was the box opened when you got them? As Turbo said if "H" has his set witht he same part number he can open the box and check for the marking on each and let us know and compare. Also look at bothand compare the color of the ring where is set in the groves. If used it should show signs of cumbustion on them and look diff from the new one. Even if cleaned it will look different. in color due to the heat.

Ask "H" if he used Turbos rings to set you piston to bore clearence and this may help clear up the ring question. If not will will go old school on the rings in the cylinder and piston crown dia in the land area.

What consernes the most is a new bored/honded cylinder and old rings that were alredy broke in on another cylinder or ran in a out of round cylinder. To much invested not to be sure. If the unmarked ring was installed and the piston siezed on it it would wear the ring badly and out of round being locked in the land. Expecially in a new cold siezure. A lot of the heat transfer is through the rings to the cylinder walls. A new cast piston with a high silacon content will resist heat transfer and leave more heat in the combustion chamber and need to be taken out the head. Remember when the piston is cold its oval and tapered so the skirt has clearence and the rings are the only thing tight in contact with the cylinder wall. The heat has to go some where. Its gota go some where. So the path of least resistance according to material porpertys has an effect on where is it goes.

Contuination:

So if the rings do do transfer as much heat where does the heat go from the crown as the piston assorbs the heat. We now that the pistonis gona take its fare share according to the alloy propertys. Knowing the piston is acting like a heat sink at this point the transfer is related to the parts in contact with it. If the rings do not transfer as much or as quick the heat builds and the piston swells at a quicker rate and or reatins the heat untill a point the piston goes beyond the engineed amount of swell and distores as it continues to swell in an uncontrollable manner. The effect of this is the piston pin locking in the piston as the piston goes out of square. The piston has filled the cylinder the most it can due to its size and cylinder shape so it starts streching up and down this being out of square and the related part suffer. Why the pin two reasons the on most important is the heat transfer is finding a way to the disapate. The pin and rod bearing,rod and crank,bearings is a source of the way out again according to the propertys and the amount of material in direct contact with the source. As the transfer accures due to ring loss effency the underside of the crown will show signs of over heating. known as flash over. This cooks the lub right off the bearing aloowing more heat transfer,need I say more. As the heat transfer increases through the rod and crank the incoming charge is effected 1 by the heat evoporation and 2 chagre strenght density then the motor (( Internal Combustion Engine ? )) leans out and compounds things. As the heat vaporation accurs it leaves the oil residue all over the bearing and lower end parts. By now you rings are tost and the combustion has blown by the rings and the enige is now cooking it's self up from the inside.

Contuination:

Oh boy. Now that we have a tasfr down the stem as I like to call it where does it go. Some of it is tranfed via the incomming cool charge ( ambient) and the rest goes right through the main bearing and into the case. Remember we have heat and lubractin loss in the main bearings We now have a metal to metal contact and there frictin to add to the load already there. What tkaes place then is the bearing starts to grow as the case are taking as much heat as they can which by the way is AL and acts like a heat sink into ambient air ( no water cooled cases out there) and can only disapate so much. The lesser wil llet go just like a piston to tight in the cylinder in this case the AL is the softer alloy. So as the bearing lock they start to spin in the case changing the path and quanity of transfer. This is when the full load is on the piston, head and spark plug and are doing all they can and it goes south quick due to the cylinder not disapating it's fare share. The Engine at this time is turing around 7,000 rpm that's 116.666 revolution a second. Yes the pisotn is in contact with the cylinder which by this time its siezing againt the wall scuffing it all to heck and taking out whats left of the ring seal locking then in and snaging one on the port due to loss of the ability to move in and out. All that can happen cold in matter of under one minute, and hot in under one second.

This is why I feel the rings are not to be over looked. That's a lot for a tiny piece of metal to endure. I could go on but I rambled enough plus I'm out of coffee. As always just some back yard hacker thoughts.

That's one hell of a post! Sorry it has been a couple of days since I last posted. But school has just started back up (currently at O-State!) and just trying to get back in the swing of things. I understand everything in your post, and will check the gaps and relate them to the marked and unmarked rings.

One quick question concerning my crank: Since this is presumably the first time this motor (( Internal Combustion Engine ? )) has been apart I think it would be wise to go ahead and rebuild the crank. I would like y'alls input on this. I look at it as this motor (( Internal Combustion Engine ? )) has been running for 25 years. That's alot of time....but at the same time, "If it ain't broke....don't fix it." I know I've been asking alot of things that could be answered myself if I had the time to get out and just clean up and work on the damn thing. Just haven't gotten to that amongst 3 or 4 other projects that I always have going on. Your help doesn't go unappreciated!

Sorry for the delay guys....I have been swamped with school and work! But I did get some measurements and did a little investigation on my .25 rings.....

The two rings I have are both stamped come to find out. One of them is just VERY faint. Neither one looks like it has been used, but one of the rings stamp is just not very distinct...so I will refer to the two rings as "clear" and "unclear".

Down bore measurements:

27.0mm down:
Clear .58mm gap
Unclear .50mm gap

40.0mm down:
Clear .58mm gap
Unclear .48mm gap

Both rings are 1.45 mm thick, or "tall"
Both rings are 3.33 mm deep, or "wide"


So now my question is should I run these? If so, which one on top....If not, I need to find another pair!

Again, sorry for the huge delay...but I don't know where I'd be without this community....Thanks guys!

still need the rings? I might have a set, I'll look for you if needed.

Tough call on the rings with out looking over the whole package and the numbers. According to the book I would say no. If the number work out than I would use the the one with the largest end gap on top. One of the numbers I'm refering to is the piston to cylinder clearence number. The clearence will have an effect on the ring end gap. As previous stated I would bank on "H" having the clearence correct and the rings are the problem. Another issue I would consider would be the the amount of free play ( piston rotation ) in the gap and and locking pin. If there is not enough free play than as the piston crown swells the rings will be forced againt the cylinder wall and cause failure. As a safe bet If mud has a set it would be worth at least getting and measuring them as a comparison. By chance do yo have the piston number you have, I will go back and re read post to see if it was posted. Most of the time as they change the piston or update it it also includes the rings as well. There may be a capatibleility issue causeing the excess number. Better safe than sorry. I will get ahold of a guy that knows more about the part numbers than I and get his take on it. Sorry I can not be more help than that.

hoser should have a set thet were too small for mine that he can try and see if they work...

27.0mm down:
Clear .58mm gap
Unclear .50mm gap

40.0mm down:
Clear .58mm gap
Unclear .48mm gap

Both rings are 1.45 mm thick, or "tall"
Both rings are 3.33 mm deep, or "wide"

Forgot to mention that the reason for the unclear /clear numbers diff was most likely the rings not square in the bore if the orientation on the gap was the same for all measurements. One can look at it two or three different way One ring or the other was not square in the bore, the orientation of the gap was or not consistent or the rings are are out of round. Since your at 40mm which I take it the ring was above the exhaust port and it's chamfer ring bulge not a factor.

I know your more concerned with the gap # but thought I should try to make head or tails out of the numbers. Another factor would be piston to cylinder clearance. If you knew the number one could be sure. A greater clearance would open the gap and the gap would be consistent with the specs. Since it has been bored rotating the rings end gap 45 degrees and re check should yield the same numbers if not than theres an indacator of bore out of round/taper. Even then there is numbes for that which is not likly on a fresh bore. If was done on old cylinder than is would tell you it's either out of round/tapered and ring wear out of round and most likly both. If new ring was used in old bore than it's an indacator of bore out of round and taper.

I have more of an issue with running a old ring in a fresh bore. This is my biggest concern. It will shorten the life of the rings and the bore. Since the two measure the same and the clearence are diff than something is off. Which is what lead to think of two differnt ring part numbers in one package based on the rings set for the piston number.

I've recently discovered something new....that could be a pisser. On my old piston I can clearly see a "25" stamped on the top. I only have a cheap-o digital caliper to do my OD measurements and a set of feeler gauges for the ring gaps. In other words I don't have any quality measurement tools to get really accurate numbers for something as accurate as these tolerances. I will rotate the rings and re-check the gaps down bore and see if they match up with the numbers I already have.

Andoh, your in Wichita right? I should have a break from work sometime in November, I could try running up there and letting you take a closer look if needed?

Mud, if you do have a set of rings I would be interested...It would be nice to do some comparison measurements.

Holy rut ru. Your old piston that was ran it that cylinder was a .25 and the new is a .25. That explains a lot. I take it your gonna compare the old rings to the new ones and see what the diff is. One is a superseded part. Be sure to keep the old piston and rings together while working with them. Also mark the top and bottom ring if removed from old piston for logging purposes and the numbers and there relationship.

I will call Stix and see if he wants to make a road trip to stillwater. The wife's can do some shopping while we play. I'm sure the piston to wall is with in spec or real close of "H" would have told you to get a new piston. I do find this very interesting comparing the pistons/rings and the part numbers. I'm feeling more comfortable about the Numbers since most likely the cylinder was honed to except the new parts and could explain the numbers. Just quesing here I now feel your probably ok just let it come up to temperature before hammer down and use a good synthetic oil in the gas.

If you measure the gap of the old bottom ring in the cylinder measure the width as well as end gaps at proper orientaion and rotate 45 degreecounter clockwise and log end gaps at top of cylinder,half way down to the exhaust port and right above the exhaust port. Be sure to use new piston to square rings in the bore. Since its a new bore/hone use some two stroke oil on the cylinder walls and wipe on the rings. If you do the old ring measure up make sure its ok to use not to scratch up the new hone.

Is the 681 piston the new one and the damaged one is the 315?

the 681 is the new RINGS and the 315 is the new PISTON. I do not have the damaged piston boxes as this is what it had in it when I purchased the oddy. Another issue may be getting the old rings off the piston without damaging their structure...the piston melted on/over the exhaust side somewhat fusing the rings in. I may be able to perform surgery and release the rings, but no guarantees.

As far as you and Stix headin my way, that would be awesome....but I would be just as willing to bring things to you to look at as well.....my school/work schedule is kind of scattered, considering I work shift work in Ponca City lol....but if needed I'm sure we could arrange something. I'm hoping to get a chance to dissect this some more this week and I'll keep ya'll informed!

-JP

I gota quiet having cold one and look at pics. Any way I have a pretty easy weak with the exception of thursday. Stix is busy saturday. Is the eskaimos joe still by the stadium.

Yep Joes is in the same location...just 2 blocks south from the stadium. We have remodeled the stadium over the past couple years, so there are a couple streets that used to go though that now don't. It looks great though! Stillwater just got a Best Buy as well....I don't know when the last time you were down this way, but there's a ton of shopping and places to go that used to not be here 5 years ago.