Frank Glatzl came over today to take apart the rail-mower Wisconsin S-12D engine to change out the piston rings since it was emitting excessive blow-by from the crankcase vent during the Dec. 10 work session at Kingsland at which we first ran it for several hours. The blow-by is caused by worn piston rings. Blow-by is bad because the crankcase vent is supposed to be connected to the air filter. If there is blow-by getting into the air filter it would foul the filter pretty quickly, allowing contaminants to enter and eventually ruin the engine.
It was about 50 degrees when we started but with a bit of a breeze, so we were glad to get the engine out in into a garage bay, where we could work without feeling cold. I drained most of the engine oil and removed the gas tank and gas tank platform the previous day to speed up our work today. Frank took the carburetor assembly off and opened up the main engine cover. I cleaned out the remainder of the oil inside the engine with paper towels and cleaned up the outside engine cover with degreaser while Frank removed the piston. The piston looked a lot newer than an original would have (this engine is about 42 years old), so perhaps a previous owner replaced it. Fortunately, the shell bearing seemed to be in very good condition, so we did have to install the new one we had ready to go. The cylinder had a bit of a lip on it which would call for reboring if the engine were going to be in daily service but for our limited service it does not need reboring yet. There was a bit of wear on the inside of the cylinder but not too much. Frank used a hone on my electric drill to clean up the cylinder so the new rings would seat properly. He then installed the new rings on the piston, using a special tool to take them off and another to put the new rings on.
I used a scraper to remove gasket material from the edges of the cylinder head and the main engine cover. We also cleaned the top of the piston and the underside of the cylinder head. Frank re-installed the piston and then we began installing gaskets. We put new ones on the main engine cover, the cylinder head, the choke mounting plate and (later) the points and condenser box. Then we closed up the main engine cover and cylinder head. Frank then opened up the timer box and removed the innards, along with the box itself, since one of the screw mounting holes was stripped. I had the pieces of a different timer off another S-12D so Frank used the best pieces from both units, including the spare timer box, to rebuild the timer. Plus I had bought new points and a new condenser set (part no. YQ-16--not easy to find) which he also installed. He will take the original timer box home with him to tap out the stripped hole and make it a serviceable spare.
Once the timer was reassembled, Frank reinstalled the carburetor assembly. We brought the engine out to the rail-mower frame and reinstalled it. Then we hooked up all the various wires and tried to start it. The engine failed to start, although it did turn over. Frank took some fine sandpaper I had in my tool box and lightly sanded the points and then the engine started (the points must have had a bit of surface corrosion). We ran it for a while and even turned on the mower deck. There were no sign of blow-by from the piston rings, so our job was a success. We did test the starter-generator, however, and it appears the generator part is kaput. I have a spare starter-generator, so I plan to swap them out and test the new one to see if it will keep the battery charged so I don't have to use a battery charger prior to each rail-mower work session. Frank took the muffler with him so he can weld several small holes or tears at the elbow. We decided not to touch the nipple mounted to the engine that the muffler pipe hooks onto, since if it were to break off, we'd have to take the engine apart and probably buy a new "jug" (the body holding the cylinder).
I am going to replace the engine wiring, step by step, since it appears well worn and in some cases, insufficiently thick for the current it should carry. Then I will switch starter-generators and see if the new one is good.
Frank took a look a my mower deck discharge cover and advised that he thinks the mowed material will not be ejected far enough from the deck and therefore interfere with the blade operation. He was of the opinion that we ought to move the cover out about 6-8 inches. I was concerned that something like that sticking out could hit something along the rail line and might therefore pose a hazard. Frank suggested that we mount the shield with a single piece of metal that has a stopnut on the single bolt that holds it to the deck. That way the assembly would pivot backward if it struck anyway, much like modern side mirrors do. So that is also I my to-do list. Another item on that list is taking off the mower deck and inserting some washers under the pivot point bolt so the belt is centered on the tensioner pulleys. But I will need some help from Derek Scott, the local fellow who helps me with the Bolens mower decks, to accomplish that. Will also need to buy some 10-24 stainless steel nuts to use on various terminals, so they don't rust like the ones currently on them.
All in all, we put in about six hours of work each on this job, but the engine is now in much better shape and should last quite a few years before it needs more work, assuming we keep it out of the rain and sun. We very glad there weren't any hidden troubles inside the engine that would have required much more work, so I guess we will count ourselves lucky.
I will bring the rail-mower to the next Llano work session on February 18, but Frank won't be able to make that session, so will be running it by myself. Will probably have to run up to Cedar Park to pick up the muffler once he gets it fixed.
I took some photos of us at work and of the engine with the main cover off, but can't upload them until I find a SIM card to fit the camera I used. I will post them later, probably this afternoon.
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