Here is the "XX" stamp on top of the original cylinder.
I should point out that the piston had the "B" stamp.
The owner of the saw (let's call him Mike to keep it simple) also noted this saw had been the test bed for the development of an RPM limited coil as evidenced by the extra hole in the back of the shroud. Mike father was an Engineer work at McCulloch, primarily in the area of electronics including the electric start saws, the fast charger for the batteries in the electric start saws, and the 170 welder as well as electronic ignitions and a myriad of other things. I have copies of at least half a dozen patents awarded to him and assigned to McCulloch.
Since this is going to be a complete rebuild, I went ahead and replaced both seals. For the flywheel side the easiest way to remove the seal is to drill a small hold and use a coarse threaded drywall screw in a slide hammer.
For the PTO side, it was a simple matter to press out the old seal using the bearing, then put everything back in place again. To simplify the task I have made a few tools since acquiring my small Grizzly lathe. While I had good luck in the past just using some sockets as tools, I discovered that trying to install a new bearing without a mandrel in the bearing to keep the needles properly aligned can allow the cup to partially collapse causing the needles to cock and the bearing to run off the shaft.
Below are the fixture to hold the bearing insert, the I.D. has a step to hold the insert and a through hole large enough to allow the seal and bearing to pass through. The driver with the smaller O.D. will pass through to allow the bearing to be pressed out, the one with the larger O.D. is used to properly set the position of the bearing and the seal in the insert.
Another tool I made is a tapered sleeve that allows me to slide the bearing and seal in the insert over the step in the shaft without risking the lips of the seal hanging up and possibly dislodging the garter spring in the seal.
Another tool that is nice to have is the driver for the wrist pin. I have done this many times using a socket but this tool has a pilot that keep the driver properly centered over the wrist pin making the whole operation a bit easier. When you are changing pistons, make sure to get the piston installed correctly with the wider skirt up towards the intake side since the intake port is wider than the exhaust port. If you get it wrong the skirts won't cover the intake port and you have to take it apart again and assemble the parts correctly.
Mark