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Honing cylinder/piston Empty Honing cylinder/piston

Post  balogh on Sun Apr 03, 2016 10:37 am

I have an old,  bit worn TD 051 cylinder and a new, double-groove piston (the one on the right on the picture below) that I want to marry to it, but the piston   is too tight in the cylinder. (It sometimes happens with newly weds.... lol! )

Honing cylinder/piston Double10

I have read on CEF somewhere how to hone cylinders, what polishing fluids like toothpaste? car polish? are best used for a smooth honing.

I am thinking about using the original, worn piston and run it in the cylinder with the help of an electric starter, putting some honing fluid into it until the new, double-groove piston runs easier.

Can you offer me any help keeping in mind that I do not have tooling more sophisticated than that? Thank you.
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Honing cylinder/piston Empty Re: Honing cylinder/piston

Post  fredvon4 on Sun Apr 03, 2016 1:30 pm

I dd two TeeDee .049worn cylinder to fit  NEW .051 pistons and it worked well

I used the worn .049 piston with rod removed on the end of a tight fitting dowel in my drill press, after I fussed about getting to to spin concentric by fussing with the dowel

clean hot (small crock pot) soapy water near so could I test fit often in dry cylinder

Held the worn cylinder in my fingers and only moved up and down (in from the bottom)and not getting too close to the very top

Set the spindle speed to slowest

Used three different grits of diamond paste 6 micron, 3 micron and 1 micron...sorry phone won't cooperate

https://www.dmtsharp.com/sharpeners/specialty/dia-paste-1/

I kept at it with the 6 until the new piston would stop hard near TDC, then a few runs of the 3  until the piston would be tight at top, and final polish with the 1 micron for a new mirror finish inside  and the piston did well at the Paul Gibeault drop test

Later I was concerned that a mirror polish inside was not going to hold oil so I did a quick swipe with Emory cloth to rough up the cylinder a bit

I imagine any lapping compound or tooth paste abrasive would work
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Honing cylinder/piston Empty Re: Honing cylinder/piston

Post  KariFS on Sun Apr 03, 2016 3:06 pm

Andras, you may be thinking about this thread:

https://www.coxengineforum.com/t7586-did-i-ruin-my-brand-new-teedee-cylinder

Ken Cook described a honing method there, I tried it, it was a success Smile

I have a couple of cylinders waiting in line for the honing treatment, nothing fancy, just plain old #2's, and I also plan to arrange a "marriage" or two.
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Honing cylinder/piston Empty Re: Honing cylinder/piston

Post  Ken Cook on Sun Apr 03, 2016 3:33 pm

Seeing that some of us are vastly spread apart, some suggestions on what to use might not be available to those across the seas. If I have to make an aggressive cut, I use rottenstone powder mixed with a lightweight 10w oil or 3 in 1 oil. I prefer this due to it washing out easily and not staying or imbedding in the cylinder. If I want to do a less aggressive pass, I prefer liquid abrasives made for silver or brass. I use Brasso but again I don't know if this is available to others.  These take more time but offer a more mirror like finish on the surfaces .  The tool I use to do this is a piece of 3/8" brass tubing. Seeing that the internal portion of a Cox piston is tapered, you can wrap a piece of tape tightly around the tubing and push it into the piston with the rod hanging inside the tubing. This allows you to rotate and move the piston up and down in the bore. Rubbing compounds work equally as well but I found these really need to be cleaned and scrubbed out with a old toothbrush. Don't leave any traces of residue on the piston or in the cylinder. Residue can easily get stuck in the ports of the inside of the cylinder. When the lapping part is complete, using a Davis Diesel wire bore brush can also assist the fit and break in as it leaves crosshatch marks on the inside of the cylinder.

To fit this new piston to your old cylinder, I would do all lapping with the piston upside down in the cylinder. Loosen up the bottom end real good and when it does slip in and out easily turn the piston back around and lap in the top without bringing the piston all the way to TDC. This will leave a good pinch up top. Remember don't go to far as it's much easier to take it apart and lap a little more than it is to go the other way. Ken
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Honing cylinder/piston Empty Re: Honing cylinder/piston

Post  balogh on Mon Apr 04, 2016 12:06 am

Thanks to all of you for the advice and links. I will try lapping/honing as you advised.
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Honing cylinder/piston Empty Re: Honing cylinder/piston

Post  KariFS on Mon Apr 04, 2016 3:54 am

FWIW, I used "Autosol Chrome Polish" as lapping compound. It smells, looks and feels like just about any chrome polish, white, kind of tooth-paste like stuff. It is a rather gentle (or fine) compound, so using it will take time.

Maybe some fine valve-lapping compound would work for the more coarse work?

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Honing cylinder/piston Empty Re: Honing cylinder/piston

Post  balogh on Mon Apr 04, 2016 4:01 am

Thanks, Kari,

I also have some car polish fluid which I will check for its sensible (or rather, insensible) grit content before using it. Otherwise, I just noted the metallic top half of an old ballpoint pen will just fit inside the double-groove piston and serve as a dowell when gently turning the piston in the cylinder while lapping. (You must be inventive if you do not have a lathe, or other machining tools back home..)


BTW I have no idea for which engine this double-groove 051 piston may have been made, but for some strange reason it is a tad wider than the stock o51 piston hence my need for honing..I just bought it once on ebay in hopes it will swap with any 051 piston which are not easy to find anywhere...
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