Author Topic: V-Twin Part III  (Read 1009 times)

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V-Twin Part III
« on: June 10, 2015, 11:54:58 AM »
V-Twin – Pistons & Rings

On virtually every engine I built in the past, I had problems with compression. However, that problem is no more since I started to use DOM tubing as the cylinder liner. For the V-Twin, I am using 1” inside diameter DOM tube (from On Line Metals). As close as I can measure, the ID is spot on, 1.000" with no taper. The inside wall is polished smooth as glass.   Following is how I make the piston, cylinder and rings:
- Make the aluminum cylinder body first but with a 1.190” bore.
- Start with a 2” length of 1” DOM and turn the OD to 1.188” for a light press into the cylinder body, and then cut it off to length. Press it into the aluminum body.
- Make the piston blank by turning a 4” long piece of 1” diameter cast iron (which is always oversize) just enough so it is a tight sliding fit into your aluminum cylinder body.
- Polish the piston to achieve a sliding fit into the cylinder.
- Bore an .910” diameter hole ¾” deep in one end of the piston blank, actually the ID of the rings.
- Part off six rings from the piston blank (I usually cut off a few extra) each about .045” wide.
- Now, cut the ring grooves as specified on the drawing and complete the two pistons.
- Using fixture A, sand (150 grit) the rings just enough to fit the width of the piston grooves.
- Using a diagonal cutter cut the rings forming the ring gap.
- Using a very fine file, lightly file the two ends of the gap.
- Place the ring on fixture B.
- With a torch, heat the ring opposite the gap until it turns red for about 20 seconds.
- Remove the ring (let it cool). The gap will remain open but will  close with a little pressure then spring open when pressure is removed.
- Now it’s a matter of putting the rings on the piston and inserting the piston/ring assembly into the cylinder. That may take a little effort.

You’re done! It took me about five hours. Hope this helps. Note: Email me for a sketch of fixture A&B.


« Last Edit: June 13, 2015, 08:40:01 AM by ernie »