liquid_TR

Attention - Thread for engine freaks!

I always wanted to know what type of compression rings are used in our 2 and 4 stroke glow engines.

Say is there a difference between the rings of a Saito 100, OS 120AX, Webra 120 and YS 110FZ?

And how to make the new rings sit and seal the old sleeve?

How to implement the full size honing process to our glow engines? Which grit to use, how to chose & do the glazing or most suited bore finish?

How to minimize the blow-by to increase compression?

Flyboy Dave

My Feedback: (21)

You can refinish the cylinder by hand and prepare it for a new ring.
Here is an example of a large cylinder S.T. 3000, and a small one,
a K&B .61. Use 150 or 180 black paper. You must use a heavy grit to
scratch the surface and remove most of the old glazing. Fine paper
will not do it right. You do not want to polish the surface, you want to
scratch like in the pictures.

I always prepare small model engines by hand for a new ring.

Most rings are made of cast iron. They break easily if you mishandle them.

martenson

Hi liquid_TR

I usually deglaze my cylinders with a verry fine grit.
It's the same one I use on masterbrake cylinders on cars.
I don't know the grit number, it's an 40 year old hone I use and it works great.

The piston rings I've seen is iron ones, eather std or dykes(L profile)

Only chrome molly on my race car engines, big 7,2 liter or 440 cui.

Good luck

liquid_TR

thanks for the replies

nice photos dave,

The idea is to remove the mirror like glaze to create "valleys" in the bore for the fine oil film to catch onto - nicely lubricating on the next stroke right?

But wont the heavily scratched surface eat the new ring (even for a short time)? actually how heavy scratching needed is the main question - and only the experienced fingers can give the answer

I get the idea of removing the glaze by heavy scratching - creating rough valleys, but then would it be a good idea to soften those serrated crests with a finer grit? would it help it or make it worse?

Kweasel

My Feedback: (29)

Take a good look at the finish on your YS cylinder at 10X magnification. Some of these are plated and will show no wear. If it looks good then just install the new ring, if the old one wore out then the new one will wear in quick enough. Call YS Performance for expert advice.

Flyboy Dave

My Feedback: (21)

The high points of the scratches wear against the ring, There is a very tiny bit of
wear on both parts when the engine runs. This tiny bit of wear on both parts allows
them to mate to each other for a proper fit. This happens in just a few moments
when the engine runs. The engine increases compression as this process takes place.

The valleys of the scratches store oil, and keep the ring lubricated and cool while it
continues to break in over time. Once the ring and cylinder wall are completely mated
and broken in, they will be shiny, and the engine will be at peak compression for a
long time.

Sometimes if you re-ring an engine and do not prepare the surface for the new ring
(de-glaze) the ring can have trouble breaking in....or worse, never break-in because
the parts did not wear together and mate the surfaces.

There are different grits of stones used for cylinders when manual de-glazing is done
....and when a cylinder is honed after it has been rebored. They vary from 150-180-220.
The courser grits are used to remove the rings cut around in the cylinder by the cutting
tool in the reboring process, and making a cross hatch pattern for the rings to seat. A
somewhat finer stone is used in the de-glazing procedure when you don't want to remove
material....rather just clean off all the glaze, and put on a nice cross hatch pattern to help
the ring seating process.

The brake cylinder hone can do a satisfactory job as well, but keep in mind the stones are
finer in grade....usually 240 grit and make a less rough finish. In the brake cylinder application
the surface partners with a rubber seal rather than a metal piston ring....so the desired
finish on the surface is not as rough.

So, the scratches cause wear and make the ring seat quickly, as well as hold some oil
to keep the ring cool. The wear is an infinitesimal amount, not enough to be a problem,
rather it is necessary.

FBD.

blw

My Feedback: (3)

You can ask Troy Newman in the YS Engines Support forum. He is good about getting back to people with good answers.

rainedave

My Feedback: (1)

I've been doing something similar to sleeves when I replace rings. If it's wrong, please tell me. I take a piece of black 320 wet/dry paper and soak it with castor oil, wrap it around my finger and scuff up the inner surface. They end up looking like the one's in FBD's photos, so I think I'm probably doing it right.

David

DarZeelon

One more issue, TR, is if the ring is designed to rotate freely in the bore, or to stay in one position.

Most schnürle ported engines use 'pinned' rings, i.e. there is a pin in the ring groove of the piston that the ring's gap is notched to accept (or a separate notch in the back of the ring in some engines).

The reason for this is the relatively wide ports that a ring end can 'catch' in, if it lines up with them while rotating...
Many older engines have even larger, multi-bridged ports. They allow the ring to 'ride on the bridges', so as not to become caught.

In this type of engine the ring is free to rotate.

Kweasel

My Feedback: (29)

I have examined a couple of OS engines that had considerable run time. One was an old 120 and the other a 108 made in the 1980s. Both liners had a ground and plated finish, and still looked very abrasive under a microscope. Pistons had some scuffing and the rings worn smooth. Im not sure if sanding the liner would have been beneficial in this case since they were already rough and nearly pristine. I normaly don't think twice about honing a steel cylinder, Im glad I took a good look at these plated ones.

liquid_TR

Ok, what about re-assembly after a maintenance disassembly?

Say If I were to disturb the rings original position and there is no pin holding its original position on the piston(free rotating).
The engine would probably loose some compression due to ring mis-position, but would the ring & sleeve break in itself again as the original position?

Flyboy Dave

My Feedback: (21)

....most likely, if you took apart a free ring engine and put it back the way it was
it would probably be just fine.

liquid_TR

Kweasel,

So the hard plated chrome sleeves either doesnt need that much de-glazing, or if they are highly glazed, they need heavier grit papers to de-glaze then a nickel plated sleeve which has a softer surface than chrome. ?

liquid_TR

Thanks for the quick reply Dave.

Flyboy Dave

My Feedback: (21)

....'yer welcome, TR....

....you need to deglaze if you are re-ringing the engine. Normally a new ring will
not seat properly unless the surface is prepared. Usually ringed engines have either
a chromed bore (like K&B) or a plain steel liner (like OS).

You must de-glaze any ringed bore in preparation of a new ring. If you don't, you might
wish you did.

The de-glazing stone grits stay the same regardless of the type of surface of the cylinder.
Keep in mind, that a chrome bore will have little or no wear, so the lighter stone would
be used. When de-glazing stones are used, they also "true up" the bore....which is to say
they remove or decrease the high spots....leaving a better, flatter, and cleaner surface for
new ring to seat on.

I have "re-seated" K&B rings on a chrome bore when the engine had overheated, and lost
compression. The cylinder wall was glazed. I used some rough paper....cleaned up, and
scratched up the bore as best I could (the chrome is hard to scratch) put it back together
and successfully re-seated the old ring. The minute (fresh) scratches were just enough to
wear the old ring surface enough to re-seat it, and the compression was restored.

FBD.