Help! Oil rings too tight?

Hi All,

Just putting the barrels back on my 850 and thought I would try to fit the new pistons, with rings (+.060), in the bores before mounting on the bottom end. Hmm, my ring clamps will not close the oil ring? Seems the spacer ring, which supports the two scrappers on shoulders, exerts a huge outward force on the scrappers. Is this normal, never noticed before that the spacer/support is compressed so as to push the scrappers hard onto the bores? I thought the spacer was simply a spacer but seems it also forces the scrappers outwards?

I can easily, remove material form the butt contact faces of the spacer ring to make it easier to compress but I don’t what to over do it and let oil get past.

PS Re-bored, new Hepolite pistons and rings, compression rings and scrappers all a good “in tolerance” fit when checked in the bores individually off the pistons.

Advice definatels needed!

Cheers

Nigel

Are you saying that the oil ring cannot be compressed enough to enter the bore or am I misunderstanding? Oil rings generally don't have much tension on them compared to the upper two rings so unless I misunderstood (entirely possible), it sounds to me like the oil rings are the wrong size for the bore or possibly the wrong style rings for the application.

In addition to what 996 said, do I understand that the pistons and rings came as a matched set together? Also make sure the spacer is not overlapped. They are usually painted with just a dab of different color on each butt end. If for instance the colors are pink and green, when assembled you must see pink and green, not just pink or green. It's also easy enough to not get the spacers seated around spacer correctly and one or both of them per piston could be sitting proud when you try to compress into groove.

mike996 said:

Are you saying that the oil ring cannot be compressed enough to enter the bore or am I misunderstanding? Oil rings generally don't have much tension on them compared to the upper two rings so unless I misunderstood (entirely possible), it sounds to me like the oil rings are the wrong size for the bore or possibly the wrong style rings for the application.

Click to expand...

The rings came with the pistons and fit the bore fine, its just that the assembled oil ring won't compress sufficiently when I put all three bits together on the piston and offer it to the bore - perhaps my clamps are too weak but seems a lot of pressure?

Biscuit said:

In addition to what 996 said, do I understand that the pistons and rings came as a matched set together? Also make sure the spacer is not overlapped. They are usually painted with just a dab of different color on each butt end. If for instance the colors are pink and green, when assembled you must see pink and green, not just pink or green. It's also easy enough to not get the spacers seated around spacer correctly and one or both of them per piston could be sitting proud when you try to compress into groove.

Click to expand...

The butt ends are not painted on these just ground The butt is visible when all three bits are assembled just seems the spacer is too long (perhaps needs shortening a little) but I have not come across this problem before. Always was room for another surprise

Regards

I have a set of 850 Hepolite pistons on my work bench

the expander spring when located in the ring groove (without the two oil control rings ) sits flush with the piston land so will easily enter the bore without the oil control rings fitted
once you fit the control rings they do expand to apply tension and pressure to the cylinder wall to seal

bear in mind the piston land diameter is smaller than the skirt it steps down just below the ring grooves and the fully assembled oil ring is always a few thou proud of the skirt

if your cylinder has been re bored to +060 the problem could be the lead / taper on the cylinders that allow the pistons to enter easily has been removed ( your bores are now 1.5mm larger than stock )
And the rings are now butting up to the cylinder bottom when you try enter the pistons ,the three piece segmented rings can sometimes be a real pain to compress in to the cylinder as they are not taper faced but when installed they do work well
check the expander looks the same size as the piston skirt when seated in the groove with no end overlap if so it should go in , try it for fit without the control rings to confirm if sizing is ok

Nigeldtr said:

mike996 said:

Are you saying that the oil ring cannot be compressed enough to enter the bore or am I misunderstanding? Oil rings generally don't have much tension on them compared to the upper two rings so unless I misunderstood (entirely possible), it sounds to me like the oil rings are the wrong size for the bore or possibly the wrong style rings for the application.

Click to expand...

The rings came with the pistons and fit the bore fine, its just that the assembled oil ring won't compress sufficiently when I put all three bits together on the piston and offer it to the bore - perhaps my clamps are too weak but seems a lot of pressure?

Biscuit said:

In addition to what 996 said, do I understand that the pistons and rings came as a matched set together? Also make sure the spacer is not overlapped. They are usually painted with just a dab of different color on each butt end. If for instance the colors are pink and green, when assembled you must see pink and green, not just pink or green. It's also easy enough to not get the spacers seated around spacer correctly and one or both of them per piston could be sitting proud when you try to compress into groove.

Click to expand...

The butt ends are not painted on these just ground The butt is visible when all three bits are assembled just seems the spacer is too long (perhaps needs shortening a little) but I have not come across this problem before. Always was room for another surprise

Regards

Click to expand...

kiwi said:

I have a set of 850 Hepolite pistons on my work bench

the expander spring when located in the ring groove (without the two oil control rings ) sits flush with the piston land so will easily enter the bore without the oil control rings fitted
once you fit the control rings they do expand to apply tension and pressure to the cylinder wall to seal

bear in mind the piston land diameter is smaller than the skirt it steps down just below the ring grooves and the fully assembled oil ring is always a few thou proud of the skirt

if your cylinder has been re bored to +060 the problem could be the lead / taper on the cylinders that allow the pistons to enter easily has been removed ( your bores are now 1.5mm larger than stock )
And the rings are now butting up to the cylinder bottom when you try enter the pistons ,the three piece segmented rings can sometimes be a real pain to compress in to the cylinder as they are not taper faced but when installed they do work well
check the expander looks the same size as the piston skirt when seated in the groove with no end overlap if so it should go in , try it for fit without the control rings to confirm if sizing is ok

Click to expand...

The expander is fine in the bore and is back from the edges of the rings when assembled so I don't think are any issues here. As you say the bore is 1.5 mm bigger now and there is almost no taper at the bottom so "wiggling in" is not really an option. I will see if I can get a big enough hose clamp and some shim steel and see if they will compress sufficient to go in. I'll work from the top of the cylinders and can then pop on the compression rings once the oil rings are in.

I think you're going to be ok. Though the scrapers don't exert much pressure when assembled, as 996 mentioned, they can be stubborn when being compressed in the ring clamps. They often want to "bulge" out of the groove at one or two locations, the nature of the space (hey, that rhymes). And ring clamps as a rule are often not that precise. When you get the piston and rings all clamped up with the pressure you feel is right, look around that oil ring assembly. Lightly tap around on the clamp with a small hammer or screwdriver handle at the oil ring location any areas that seem to not be compressed. The weird little bends and waves in the spacer don't always want to compress equally under the scrapers and may need a little help.

This just dredged up an old memory.. I bought a Wiseco 1196cc big bore kit, (Yam XS11) the oil rings were supplied the wrong size, everything else, was correct. JFWIW

I've had exactly the same issue with two engines now.
These were Hastings rings (supplied with new 'Hepolite' pistons)and all the rings themselves were spot-on and didn't need gapping.
However, the separator element of the oil ring needed a good amount removing before it would allow the oil rings to sit correctly.
I'm not sure if they're supposed to exert any outward pressure, but these were bigger than the bore.

It seems your experience exactly matches mine.

Incidentally, the engines in question don't smoke!

Guys you were bob on – super stuff!

Well, I put my nice expensive ring claps to one side and went back to the baked bean tin and water hose clips (actually used some brass shim sheet). Last time I used this method was 35 years ago. Anyway, went in from the top just the oil rings first, nipped up the hose clips tight to the barrel top and then backed of a little, used the blunt end of the hammer to knock the piston down and “bingo” in they went. Interestingly, I could hear the “tap” tone change as the scrapers went into the bore! One sounded as if it was just catching the top of the barrel, so nipped the screw up a bit more on the clip, another tap and they were in! The compression rings, seeing they had no chance of resistance, just dropped in afterwards.

Putting the gudgeon pins in from the bottom was also easy once I made up some "long" threaded studs to hold up the barrels (used 8mm stud rod) and put these into the stud holes where the long hex bolts normally go. Used some nuts to hold the barrels high - also enabled me to finely adjust the height so that I could line up the pins, pistons and rods. Heat gun for a bit of warmth and in went the pins while sitting comfortable on my workshop chair! The rest, easy as eating chocolate cake I will definitely do this in future.

Great end to a frustrating – Thanks

PS pistons and rings are in “dry” apart from wiping the bores with a cloth and some WD 40!

sorry - Great end to a frustrating day!!

There are some oil ring expander units that have color-coded ends, and you CANNOT trim them! (nor can you overlap them)

The oil scrapers sit within thin shoulders of the expander and have to be installed in a very exact manner.

It's all so wonderful...

http://www.youtube.com/watch?v=PyUjvaQa2h0 lookey Here .

conversely , some of this type ,
the ends ARE designed to overlap / engage .On the ones that press out from behind the scraper upper & lower , which are marked
TOP & perhaps bottom ( inside ) as some are outer face and inner face and should be fitted thus .

So reading the supplied instructions , & inspecting the flat oil rings under a strong light as to markings - which will be at the END ,
Also the tension ring as to if its designed for the ends to key together maintaining its correct radial depth .

Haveing virtually never used ring compressors , just fingernails Compressing them isnt really the game . Its HOLDING them Compressed .
Sometimes ive used card or tin sleeves & rubber bands . Unless someones thrown decent ring compressors at me .

The trick with the sleeve is to engage it near dead square , catch a edge in ,( half way :shock: ) and feed the circumferance bilaterally ( both sides working round)
on a good day they jump in .
A good analogy is a Clutch / Gearbox spline . With the plate centered before tightening the cover , the bellhousing dead parrallel to the block face ,
it Jumps In . At Wortst - in 2nd - vice grips on the output shaft , a finger to rotate it and it 9 spline ) engages with a CLICK .
just explaining that as the tecniques similar . The Dang thing HAS to be pretty much dead square / parrallel faces . Or you get hung up .
this is painfull therefore best avoided .

A selection of timber rods from the same stock ( four or two of each ) in various sizes - to support the barrel keeps things steady . Rocking & rollings
Not On , There .