Chainsaw Repair

I didn't get here tomorrow, today is the day after tomarrow, but I did hone the piston rings I needed to sharpen on tomarow.  Two of the three cylinders are getting new rings, the ones I'm reusing are the two in the Poulan 245.  They're angled face rings, I can see the angle but I didn't know what angle it is.  They're widest at the top. 

What I did was coat the surfaces with blue layout fluid.  Then I cut a strip of paper from a Right Aid cash register ribbon.  It is very tough thin paper, 0.002 inches thick.  It's ideal.  I cut a two inch long by 3/4 inch wide.  Then for the first trial I folded one end on itself 1/8 wide. I placed that upside with respect to the fold down on the hone.  The hone I used is a medium oil stone, a six inch long stick, one inch wide shaped like a wedge with a 1/8 radius on one edge, a 1/4 inch radius on the other. I'm using the flat so a rectangular four or six inch pocket hone will work fine, use the fine side. 

I laid that fold in the paper down on a spot which looked smooth and flat, the area just beyond the fold is the part of the hone which will be used.  The piston was set on the paper with the ring grove just overhanging that 1/8 inch wide end which has been folded over.  the skirt of the piston was resting on a single layer of paper.  The piston is set at a slight angle due to that.  0.002 rise over approximately 1.000 run, that is 0.11 degrees.

Then I held it down and rotated the rings around once.  My first guess was good enough, the blue dye was wiped away all the way across the edge surface of the ring.  To test that I reapplied the dye and laid the piston down on another strip of paper without a fold. It only removed the dye from the top edge of the piston ring edge.   Then I folded it's end twice and it only removed the dye from the bottom edge of the piston ring edge. So one fold, 0.11 degrees is the correct angle.

I returned the one fold strip of paper to the hone, set the piston ring down and used rubber bands to lash it in place.  This is a good time to mention that I placed the piston ring pin in the side of the piston which keeps the rings from turning to the top so that the rings when expanded would pass over it without hanging up. 

The piston holds the rings at the correct angle while I grasp the rings with my finger tips and rotate them around and around. Some practice is necessary the rings have to be held round.  round with most of that gap still open to where it springs out too when the piston is pulled out of the cylinder.  Once one develops that knack, it goes smoothly and well.

From start to finish it took me a half hour.  Those rings look nice and they have no nicks left on their edges.  That's sharp.