Hone This

[Richard Haight]

As Pete Muller has mentioned, the crosshatching of the honing is to provide for (A) slight retention of oil, (B) a small amount of actual surface area, which will erode slightly, "Wearing - in" to match the piston and ring.

The finer the stone, or grit of the hone, the better the seal, "All other conditions being equal".

The whole idea behind "Nickasil" or other types of "Hard Chrome or plated cylinders, is that the actual cylinder is aluminum, and therefore, it expands at a similar rate to the piston. Mercedes Benz pioneered cylinders of this type in the 1950's with the 300SL engine. Their cylinders looked like the surface of the ball in a ball point pin tip. Very hard material, with microscopic pores, or pits.... which retained oil.

Most modern cylinders that are "Hard Plated" use a proprietary process, somewhat like Kawasaki's. The aluminum cylinder is placed in a fixture, and wires of various materials, like nickel, chromium, and other rare earths, are suspended down the center of the cylinder. Then... very high current electrical charges are applied to the wire, until it begins to explode, and causes it to be deposited (electro-deposition) on the surface of the aluminum cylinder bore. The cylinder is rotated as the process of electro-deposition continues, and the materials which are deposited, are like hardchrome or Nickasil, only better!

Then, the cylinder is honed to size. It is an extremely fine hone surface, and holds oil at the molecular level.

Even newer, is the process whereby the cylinders are plated/coated with a mixture of metals, and ceramics/composites, like the Honda RC-51 (World Superbike Competition).

Yamaha's however, are older (and cheaper) technology, and have an iron cylinder liner. The crosshatching gives the cylinder a surface which holds oils, and allows the piston and cylinder to wear in to each other. You could hone it with all horizontal lines, and the rings would "Catch" on the ridges as the piston traveled up and down. Or.... you could hone it straight up and down...... and the rings and piston would wear groves as they traveled up and down in the cylinder!

The crosshatch is simply a compromise which allows for the even "wearing-in" of the cylinder to piston/ring.

You could Nickasil a cylinder, and have the entire surface polished like glass, but it would not retain enough lubrication on it's surface to allow the ring to slide..... and the smooth surface would probably not enable much compression either.....

Each type of cylinder needs a different type of ring material and tension. Iron rings (soft, and wears in quickly) Chrome-Moly (needs a finer hone), Spring steel, Over-lapping or "Total Seal".....

[Pete Muller]

[Jordan Chong]

we just had our cylinder re-honed and new piston and ring installed (Yamaha)
piston clearance was .003
ring gap was .012 (when placed into the cylinder)
does this sound right or should the ring gap be less?
regards
_________________
JT
Jamaica Karting Association
Rotax International #88

[Pete Muller]

Ring endgap is pretty much meaninless as long as you have "enough".

Definitely .010+ is fine.

You can grind the ring to have .030... and you will not see a performance difference -- I can absolutely guarantee that.

What is important is how the ring fits, and how much tension it has.

PM

[Walt Gifford]

You don't hear much about the side gap. Too much will cause ring float. If I remember, it should be less than .002" so, don't go crazy lapping those rings.


Giffy
_________________
FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

[Pete Muller]

Definitely! - good point.

The tighter the better.

Sort through all the rings you have access to and find the thickest/flattest one that fits the bore correctly.

I believe the ring tends to "cone" as it goes up and down the bore (if it has excessive clearance in the ring groove) which excessively "barrel-shapes" the OD of the ring during running. That definitely shortens the life of the ring.

PM

[Martin Secrest]

Hey, over a thousand views of this topic. I'm printing it off for the notebook.

Good stuff from the techno dweebs.

[Jack Burroughs]

Pete I've been lapping my rings on a surface plate for yrs., using a homemade fixture like the one MISI sells, with good results, my question is have you ever heard of using Bon-Ami scouring powder on ring and piston combo to lap in place? used it long time ago on Mrecury racin' outboard motors with good results. I noticed in the post about cross-hatch that you mentioned the word "Gall", I think you should have explained just how close "Gall" is to "Stuck", 'cause in my findings , once metal starts transfering it don't stop 'til things are real expensive to repair.

[Pete Muller]

[John Mulvihill]

Hi Everyone,

I've heard a lot of references to 'Ring Tension', but I've never heard a good explanation of the tension that we should be looking for.

I'm assuming<LOL> that there should be a very slight drag when pusing the ring up and down the bore with the piston?

Thanks in advance for the input and insight.

John

[Pete Muller]

What I did when I was seriously into Yamahas:

After I had all the prep work finished (bore honed, ring lapped, everything clean, etc.) I would measure how much force it would take to move the piston through the bore (ring installed), by using a fish-scale. I'd write this down in my "pre testing" notes on building the engine.

It didn't take too many tests to figure out what was the correct ring tension.

I can't remember how many pounds/ounces was a good number... but I remember it making a difference (then again... pretty much everything makes a difference once you start looking closely).
_________________
Muller Machine
How-to pages, tech documents, & more
Ultra-precision machining/blueprinting for engine builders

[Steve O'Hara]

Geez Pete,

I never realized you worked so hard on those Kt100s! I never lapped a ring or used torque plates when honing, ran about .005 to .006 clearance, tuned the suckers to run about 475 on the Digitron and held my right foot down for 60 minutes...

Did have to change pistons every race though. LOL

Seriously, on the McCulloch engines we used a very fine hone with minimal cross hatch since we used the Hartman tool steel rings. Because the rings were soft we didn't need to make the finish of the bore into a "ring grinder" and the break in period was one easy lap around Ontario. I personally have never believed that the cross hatch has much influence on the retention of oil on the surface of the bore nor do I think there is any real need for it. The cylinder is getting sprayed with oil 200 times a second and I don't think you want it to stay there very long or it will burn on to the surface and interfere with good ring seal.
SSO

[Walt Gifford]

Come on Pete, was the ring tension more or less than a stock ring?

I've heard of formula Y engines you had to put a screw driver handle under the rear wheel so they wouldn't roll away 'cause the ring was so loose.


Giffy
_________________
FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

[John Mulvihill]

Hi Pete,

Do I need a small fish scale or a large fish scale?

From Walt it sounds like a pretty small fish scale. Ring tension must be pretty low.

Anyone have any numbers to get me into the ball park?

Thank you,
John

[Walt Gifford]

I would say if there's a fish involved, the story will get better as it goes.


Giffy
_________________
FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience