With the pliers, grasp the end of the spring keeper... 

...and twist in a clockwise direction while simultaneously pull outward...

...and out she pops.

You can clearly see the end of the wrist pin now.

To press the pin out, get a foot of 3/8th's ReadiRod, a couple Heavy fender washers, nuts, a 3" piece of Schedule 40 3/4" PVC pipe and a 15mm deep socket.

Put it together like so...and turn the socket slowly through the piston. It should go through smoothly with little effort.

You can turn the piston to take a peek on progress. You can see the socket in the left oil hole in the rod small end.

When the pin is clear of the rod arm small end...

...you can slip it right off. If you are replacing the pistons you can continue to press the wrist pin all the way through.

There is an "arrow" stamped into the piston head. This arrow always points toward the front of the engine.

The piston is also stamped with the "size". It will either be a "A", "B" or "C".

The front face of the cylinder will have a corresponding "size" stamp on it's front face also.

Here's a profile of the piston in which you can see the top 2 compression rings and the bottom oil ring.

Find the gap in the top ring and peel it off.

One down, two to go...sort of.

Remove the second compression ring the same way.

Notice this ring has beveled edges and a "dot" stamped near the bottom gap.

The bottom ring called the oil ring consists of 3 pieces. Remove them in the same manner as the other 2 rings.

A picture of the engine sans cylinders, pistons and timing gears.

Cleaned piston ready for new rings.

There are 3 different size pistons for the  URAL; but only 1 size set of rings. There is no need to off-set the ring gaps, this is an old wife's tale. Later, when installing the cylinder, we'll line them up together.

Put the oil ring on first. It consists of 2 flat rings and a wavy ring.

Sandwich the wavy ring between the 2 flat rings in the bottom groove.

Bird's eye view of the first oil ring in place. Finish putting the other 2 oil rings on

Next comes the lower compression ring. The small "dot" stamped at the end of the left part of the ring always faces up on the piston.

Profile view of the oil and lower compression ring in place.

The top compression ring can go on either side up.

Finished piston.

Get the wrist pin press ready...

...along with the wrist pin.

Use a little motor oil to lube up the wrist pin and pin hole.

Start the wrist pin through with finger pressure or a couple light taps with a hammer. Just enough to seat it and set up the press. Press it through until it clears the groove for the wrist pin keepers.

To get the keepers in, put the tab in the groove at the 6 o'clock position while applying finger pressure at 12 o'clock...

...grasp the tab of the keeper and rotate the keeper clockwise while continuing to hold downward finger pressure.

The keeper will pop into place in about 1/2 a turn.

Both pistons reattached awaiting cylinders.