New rings to install - what order?

[rockin411]

I purchased replacement rings for my 1977 Yanmar SB12 engine and they're different shapes than the description in the service manual. They're Yanmar and I can figure out the oil ring but the others aren't clear.

The 3 others are:
Green outer color with a yellow mark and Tp labeled on the top.
Silver outer color with a red mark and a dot with T labeled on the top.
Black with Tp3 labeled on top

The green and silver appear to have a square profile and the black has a bevel on top and cutaway on bottom.

Also the gaps are different on all, Smallest gap on silver, followed by green then black.


https://www.flickr.com/photos/133520...posted-public/

[Lepke]

Ask Yanmar. I've never seen any rings on any engine that weren't gapped the same.
The engine spec's should have the gap. A parts book may id the rings.

[Capt Ralph]

Time to ask Yanmar.
Thru several models and newer engineering, different shaped rings have happened to many mfg engines.
There should be a service bulletin on your new set but you won't know all for sure till they respond,, with the answers..


I do remember one rep telling me they came packaged in order and not to mess up that order in a wrap or box.

[Wotname]

It is probably too late for you by now but they should have come packaged in the correct order.

I have found the YSM manual generally gives better detail than the earlier manual for the YSE, YSB and SB models. The piston, rings and sleeve is the same for of these models.

Are you measuring the gap using the technique as shown in the manual?

See attached screen shots from the YSM manual

[Wotname]

The marked side should be uppermost (towards the head on an horizontal piston).

From your description, the black (marked with Tp3) should go closest to the oil ring with the Tp3 facing towards the head and the cut away towards the oil ring.

You should be able to detect slight differences between Green and Silver by using a imagining glass or loupe etc. Look carefully at both the inner face and the exterior face.

My GUESS is the Green is the top ring.

From the parts book.

[Rumrace]

Brilliant Wotname. Well done

[rockin411]

Which parts manual is that from? That doesn’t look like mine unless I overlooked it… but i think I almost have it memorized at this point. I went with silver then green simply because I couldn’t see a difference in the profile and the silver was marked T with a dot. Most of what I read was the dot was “usually” the top… hopefully my gamble won’t mess me up stay tuned!

[Wotname]

^^ YSM parts break down book - unfortunately it don't have the part numbers in like a proper parts manual.

As for the gamble, you got an even bet

Regardless, it will work either way - for awhile

You could always get another sets of rings, have a look how they were packaged and then return them unused or perhaps better ask the supplier to check it for you.

Anyhow, hope it works out well for you.

[Wotname]

BTW, does the ring set package have a Yanmar parts number?

One of the 'joys' of rebuilding old long discontinued engines is trying to understand the various changes that have occurred in the past (as Capt Ralph alluded to upthread).

I note my SB parts manual shows a different arrangement of rings than what you have described in your package.

My SB parts manual shows the top ring with a unique part number and the next two rings with the same part number.

My YSE service manual shows the same information as the SB parts manual and shows the edge profile of the rings.

This differs to the YSM service manual description shown upthread yet the piston and sleeve of the YSE / YSB / YSM / SB are the same.

None of these manuals match exactly with the parts you have received as per your description. Going by your description, the black ring matches the third ring of the YSM service manual.

Update - I have just opened the pictures in your first post - they weren't visible to me initially but they are when I am looking at the "reply to" page - I guess there is some setting in my browser that blocked the images.

I can see a definite difference between the green and silver rings. The silver one (marked with a T) has an ever so slight bevel on its top edge and it might even have a similar tiny bevel on the bottom edge. The green one does not have these tiny bevels. The two tiny bevels sort of replicate the profile of the top ring as per the YSE manual and whose part number matches the part part of the top ring in the SB manual.

So my somewhat better educated guess is now -

Silver as the top one because of the tiny bevels and because of your comment of 'dot was “usually” the top'

Then green because its profile and because there is nowhere it can go.

Finally black as its edge profile matches exactly the third ring in the YSM service manual.

Problem solved - drink beer (or beverage of choice ).

[Wotname]

I'll go on a limb here and speculate that the green ring does not have a square profile, rather I think it might have a minuscule taper. I sorta remember the #2 ring I installed in a YSE had such a taper that I couldn't see but I could measure with a micrometer. I can't remember the numbers but it was only a tiny difference.

Have a look at the attached diagram, At first glance the green and the black look the same but look closer and the green has a taper on the LHS.

I think the green ring might be the same.

[skipperpete]

Call me old fashioned ..... but isn’t it usual to compare the rings that are already on the piston with the rings in the box.

[Wotname]

Originally Posted by skipperpete

Call me old fashioned ..... but isn’t it usual to compare the rings that are already on the piston with the rings in the box.

You are old fashioned SP .

• you are a professional, us amateur shade tree guys like to do it the hard way.
• on a 45 year old engine, you never know who or what has been in there before you; no guarantee the previous guy did it right either.
• service bulletins and manufacturer support ended yonks ago, you have to deal with whatever lands in your hands. Try getting parts after Yanmar tells you they aren't available but then you find identical(?) parts are available from India / Indonesia / Phillipines / Taiwan and still being used in rice harvesters or irrigation pumps; but they aren't quite as identical as you hoped or maybe they are or...
• pull the engine down, remove one broken ring and break another trying to get them off a gummy piston. Knock the bits off the bench and sweep then up. Wait two weeks for the new ones to arrive and rip open the pack in excitement only to realise the next day the packaged order was important.
• turn to the net and get help from CF but the other guys are around the world and use amateur terms and product names unfamiliar to the local English language.
• promise yourself you will be more careful next time and remember the professional compares the old with the new

These are some of the reasons why the professional guys knock back work on old engines but the joy of getting it running by your hands (and bugga all tools or training) under a shady dock is something they never experience...

Now did I tell you about the time I found Yanmar had (50 years ago) incorrectly assembled....no wait, that's thread drift and one for another day

[skipperpete]

Thanks for some much needed humor Wotname, I’m in the middle of rebuilding a 2GM20 and nothing’s going right, I needed a smile[emoji4]

[Wotname]

Originally Posted by skipperpete

Thanks for some much needed humor Wotname, I’m in the middle of rebuilding a 2GM20 and nothing’s going right, I needed a smile[emoji4]

You are welcome!

Sorry to hear the Japanese machinery gods are cranky with you Skip; on the off chance it helps, last night I raised a dram of a single malt Suntory along with a homage to St Patrick on your behalf.

Sláinte is táinte

[skipperpete]

Well the Suntory seems to have helped, after a rocky start( the rocker oil feed pipe was rusted beyond repair, valve lifters stuck, governor shaft o ring hanging out) I removed the oil pan to inspect the bearings and the conrod shells are brand new Std so it seems it’s been rebuilt and only test run the left alone in the rainforest for 10 years . Now if you can help with the snake problem here I’d appreciate it. The recent heat wave in FNQ bought out the taipans around Innisfail to breed. Crocodiles behind the house, Cassowaries in the forest in front and taipans on the road..... poor choice of venue for engine work.
Pete.