Break-in a rebuilt engine?
 

Hello all:
I recently rebuilt my OS 1.08 engine. I replaced the piston, both bearings,cylinder head,gaskets,etc.
Do I need to break-in the engine? I did not hone the cyl sleeve.


Tom

RE: Break-in a rebuilt engine?
 

Of course you should give the engine a short break in procedure with some extra oil in the fuel. If you use the same ring it will fit with the sleeve and the engine will develop its full power very soon. Just give the new piston a little running time to seat properly to the sleeve.
It is very usual that manufacturers recommend a run in every time after taking the engine apart and reassambling it. This may be more important for non ringed enginges.

RE: Break-in a rebuilt engine?
 

oops:
I replaced the ring as well as the piston. I ommitted this in my original post.


Tom

RE: Break-in a rebuilt engine?
 

In 1/1 Engines a sleeve should be honed if new piston ringes are mounted.

If the used sleeve still has a honed surface it will also work. The biggest possible disadvantage is that the engine will not reach its full power.

RE: Break-in a rebuilt engine?
 

Thanks, but I've never seen a (new) honed cyl sleeve. What am I supposed to see?
The top of the sleeve looks the same as where the piston ring has worn it!
Is it supposed to be kinda rough looking or smoooooooooooth?
Please excuse my ignorance, but I've never broke down an engine before.


Tom

RE: Break-in a rebuilt engine?
 

You don't need to hone the sleeve. You'll most likely just ruin it if you even try.

You should knock the glaze off the cylinder. Easy to do with a scotch brite pad and some toothpaste. Just spend about 5 minutes LIGHTLY rubbing the cylinder with toothpaste and the pad. A couple tiny drops of water in the paste will help to thin it down a bit. Rinse well in warm water and re-assemble with lube.

Don't get in there and rub the heck out of it. You'll scratch the cylinder. Thats a BIG NO-NO. Just run the pad in there and lightly work the paste around.

You really won't see much material come off the cylinder. The paste will just turn a little brown.

RE: Break-in a rebuilt engine?
 

... and I've never tried to describe that to somebody in English. I can't give you guarantee that it is understandable.

You should still find the crossed marks of the honing on the surface. It normally feels smooth even when new if you touch it with your fingers.

If an engine is new the honed surface provides a defined friction on the piston ring. After the run in process is finished, the piston ring has 100% contact with the sleeve. That gives maximum compression and in result maximum power.

The honed surface will remain and can keep an thin "coating" of oil. Visually there will be no difference to a new sleeve. If there are some areas where no honing marks are visible this is not very good.


To prevent any mistakes because of my poor english skills I have some English links, which can inform you very well about the break in process of an ringed engine and how this ring/honed sleeve thing really works.

http://www.lycoming.textron.com/main...neBreakIn.html


http://www.mototuneusa.com/break_in_secrets.htm

http://www.stealth316.com/2-breakin.htm

Now it comes to my model engines. I rebuild a few very rusty or very used
(or both :eek: ) engines. I used a Method which sounds a bit hard and
unprofessional but it works for me and I do not recommend it as the best solution.

I use sandpaper (400-800) to "emulate" the honed surface on the sleeve
(also on the bushings if necessary... sometimes also before I run an China
engine first).

It worked out very well for me. Of course you have to clean the parts very
well and don't remove to much material. Just scratch the surface a bit so
that it looks like the picture shows. Roll the sandpaper and turn it so the
scratches are crossed in the same angle like the original honing.

I repeat: This is an unofficial private method. I give no warranty.

RE: Break-in a rebuilt engine?
 

Stoneweapon....

....the info in those links are just great about rings "wearing in". You can do it
in 10 minutes.....or you can do it with 2-3 gallons of fuel on the bench.

I always get a kick when a guy says he did a careful "bench run-it" with a 4-stroke
engine.....and got a reiable idle after two gallons....

....very funny stuff. [sm=bananahead.gif]

FBD. :D

RE: Break-in a rebuilt engine?
 

Honing a modern model engine liner or even scuffing with anything abrasive at all sounds like bad advice to me (unless it is a steel, unplated sleeve). I believe all modern cylinder liners are now plated with either chrome or nickle, and polished at the factory to the specs needed for optimum running. The engines were made to "break-in" by running. Follow the mfg's recommendations and you won't have any problems.

Honing was for steel sleeves to remove bore marks/ridges from machining, and to give a smooth surface with just enough bite to wear the iron rings in correctly.

RE: Break-in a rebuilt engine?
 

I would like to read the information in the links that Hobbsy deleted.

Dave, can you pm that info to me? I wonder if a lack of hone/hatch marks in my 155 is what took it so long to develop compression or if it was that the valves had needed to be lapped.

RE: Break-in a rebuilt engine?
 

In the real World, deglazing cylinders and "surfacing" them after they come
out of the boring-bar (bored out to a larger size) is done with stones at
around 220 grit. We used 180/220 where I worked. The one with the balls
of abrasive (on the left) is called a bottle brush.

http://www.hastingsmfg.com/Service%2..._deglazing.htm

This is a good article about deglazing. The ball type stones have an added benefit
in that they radius the edges of the ports to help keep the rings from catching
on sharp edges. You run them clock wise, then counter clockwise with the
drill motor to catch both sides of the ports.

FBD. ;)

RE: Break-in a rebuilt engine?
 

The answer is....when you re-ring an engine, you de-glaze the cylinder wall.
This leaves fine scratches in the surface. These scratches rub against the ring.
A small amount of metal is removed from both surfaces the instant the engine
is started, and the first couple minutes of runnig. This is called the "mating" of
the ring.

If the surface is glazed, or too smooth, it will not break-in properly. You will
end up with lower compression, and lower performance from the engine. In
a wet sump engine you will have excessive oil consumption because the ring
never seated properly.

Even chromed cylinders are factory honed to finished size, and left with small
scratches in them. These types of engines generally use a soft cast iron ring
so the parts will mate. If a hard ring, or a chrome ring was used on a chromed
cylinder wall....it would never seat.

So the answer is....yes, the surfaced needs to be scratched up. The more
scratched up it is, the better and faster it will seal.

RE: Break-in a rebuilt engine?
 

FBD,

Have you seen how nice BME does the 110 cylinders and rings? If I remenber everything is cross hatched including the rings, this could be bad memory.

RE: Break-in a rebuilt engine?
 

No, I haven't seen the BME offerings, but I can imagine they are quite nice.

RE: Break-in a rebuilt engine?
 

All:

We have a misused term here folks. "Honing" is to cut metal from a cylinder bore, and bring it to the finished size. Unless you are doing an overbore, and installing a piston of a larger diameter than the original, honing is a very bad idea.

"Glaze breaking" is an entirely different thing, and is highly recommended before installing a new ring or rings in the original bore.

If you are using a "Brake hone" one pass up and one pass back is all that is needed. Using 400 grit paper with oil will do it in 30 seconds.

It is not necessary to cut any metal out, and it is a bad idea to do so.

If you can see even the mildest of scratches added you have done enough. Any more is artificially induced wear, shortening the life of your overhaul and making cylinder sleeve replacement that much nearer in your (and the engine's) future.

Bill.

RE: Break-in a rebuilt engine?
 

I purchased two ross twin engines years ago that had cross hatching. When I broke them in I did it old school. They have very, very good compression, not just for a dykes ring engine. I recently picked up a "nib" four cylinder, no cross hatching. :eek:

RE: Break-in a rebuilt engine?
 

There is a difference in what we would call cross-hatching, depending on
the method of manufacture. Cylinders that are honed to size with precision
hones usually show less cross hatching simply because the finish hones are
finer than the hones and bottle brushes that are used to resize cylinders in
a small repair shop.

The new cylinders that are honed to finished size do have the cross hatching,
but it is harder to see. Cylinders that are bored to size have ridges cut into them
like an old 45 rpm vinyl record. The rougher stones and bottle brushes are used
on these to "take down" the evenly spaced ridges, and effect the cross hatch pattern.

Also, the "honed to size" cylinders have a smoother surface to start with, and don't
require as heavy a cross hatch.

FBD. ;)

RE: Break-in a rebuilt engine?
 

Dave:

I don't know of any GOOD machine shop that will go to a cylinder's finished size with a boring mill. The resuktant surface is so rough that it not only cuts the ring to seat quickly, it grinds aluminum from the piston skirt. The "Overhaul" doesn't last very long. The final sizing should always be done with a hone.

Bill.

RE: Break-in a rebuilt engine?
 

Bill,

You might want to re-read Dave's post. You sound like you are argueing with yourself.

RE: Break-in a rebuilt engine?
 

I think Bill will agree with this, that the Saito cross hatch does not seen to disappear. Similar to what FBD says the crosshatch is very faint but stays there. On most of my Saitos, when you want it on TDC you have to loosen the glow plug or wait a long time for the compression to leak down.

RE: Break-in a rebuilt engine?
 

Dave:

Agreement.

But when I'm going for TDC it's usually messing with the valves and I have the rocker boxes off. A slight push on either rocker relieves the pressure and lets me get there easily.

Bill.

RE: Break-in a rebuilt engine?
 

All this talk about ball hones and boring machines------------

I would not even dream of taking a hone to a chrome plated glow engine cylinder. Thats why I use the scotch brite pad and toothpaste. It doesn't scratch or leave any marks at all. All it does it work loose the glazed on castor oil and polish up the cylinder a little bit. Usually takes about 5 minutes.

According to some very knowledgable folks on this board--you don't need to hone a chrome or nakasil lined cylinder. It's a factory plated system and is as perfect as it can ever get. And if you did run a hone down in it--you'd most likely ruin the cylinder because the plating is only a few thousandths thick. The new ring will seat on that chrome plating if you just knock the burned on castor off it (glaze)

I'll stick to the toothpaste and scotch brite pads.;) It's worked in the past on a ST .90 engine and an OS46FX-Heli engine.

RE: Break-in a rebuilt engine?
 

Pile:

You're right. I didn't even think about plated bores in my earlier post.

A plated bore MAY be cleaned, a plated bore MAY NOT be sanded, honed, or ground by any method if it is expected to live beyond the initial starting of the engine. The safest thing is to use a solvent, and not even toothpaste on it.

Bill.

RE: Break-in a rebuilt engine?
 

Bill....

....plated bores are honed just like any other bore. Look at the cross hatch
in the Chrome Saito bore....the chrome K&B cylinders are honed as well.
The honing is for the last "sizing" of the bore, and for the little bit of abrasion
necessary to seal the ring.

Motorcycle chrome bores are honed as well. They would never break in without
some friction with the new ring.

Honing or deglazing does not hurt the cylinder wall, it is necessary. It only takes
about 20 seconds to deglaze a cylinder with a bottle brush type hone, in a solvert
tank. If you had bored out a cylinder, and it was too tight (not enough clearance)
it takes about 15-20 minutes to hone out .001 (one thousandth).

It would take forever to hone .001 out of a chrome cylinder, if you could cut it
at all with a hand hone. Even a chromed bore should be deglazed and scratched
when re-ringing. Chrome bores use soft cast iron rings.

Trust me, you cannot harm the cylinder wall. ;)

FBD. :D

RE: Break-in a rebuilt engine?
 

Dave:

Of course a chromed bore is honed to size at the factory. They use very special hard fine grit stones to do it. While plating can be controlled tightly, the control isn't that tight, and the finish sizing is definitely done with a hone. But it's seldom more than a small fraction of a thousandth inch.

I'll admit I sometines give a chromed bore a light touch, but only when it has vertical scores. All I'm trying to do is be certain there is no upset metal at the sides of the scores. The original hatching pattern is still there, as you said, no more needs be done if there's no scoring.

Bill.