After 35 years of reliable operation, the Kohler engine in my John Deere 316 was beginning to burn a little bit of oil. About a quart every 3 or 4 hours. So, I decided to overhaul it and bought a kit which included a new piston, connecting rod, and valves. Step one was disassembling and cleaning the parts. The engine was much dirtier on the outside than on the inside.
I stripped everything out except the main bearings. Since most of the bolts were oil covered and a little loose when I removed them, I cleaned every bolt and their corresponding holes.
How do you remove the cam? The cam rides on a shaft that is about 1/4" diameter. It goes in the black hole to the right of the crankshaft hole in this picture. Drive the shaft out from this side with a soft punch.
This is a solidly built engine, and weighs somewhere around 90 pounds when assembled. Once disassembled, the bare block was easy to pick up and turn over to clean. Surprisingly, every internal part measured equal to new specifications. With the exception of the piston and rings, there was no measurable wear on the crank, camshaft, cylinder bore, and valve lifters. This was good news in that it was not necessary to bore the engine and use an over-sized piston.
The camshaft shaft will come out of this hole. You should not have to hit the other end of the shaft very hard.
This engine does not have the balance gears present in some versions, and from what I've read, generally discarded by engine overhaulers.
I decided to replace the governor gear, even though like everything else, there was no wear visible. However, the gear is plastic, and I once had an 18 HP Briggs & Stratton self-destruct because it's plastic oil splashing gear failed. Since a governor failure could result in a destructive overspeed, I felt it was a good idea to change it.
However, that greatly complicated the rebuild, since I had to remove the camshaft to access it. As you can see in the picture on the left, it is located deep inside the engine, above the camshaft. Removing the camshaft requires removing the bearing plate, along with the crankshaft.
oil pan was one of the easier parts to clean.
The front main bearing. these massive ball bearings were in great shape.
Finally, the fun part. Reassembly. Here is the camshaft installed, and note how the governor gear is not even visible anymore.
The timing marks are hard to see. Here is a view through the fuel pump opening. The tiny dot on the cam gear lines up with the line cast into the crankshaft.
These pictures were taken with my iPad, which has an impressive ability to selectively focus exactly where you want it to. The iPad was also useful for reading the rebuild manual.
The alternator coil and bearing plate. Once again, this engine was very tight, and I had to use all three paper spacers to get proper clearance between the sides of the bearings and the crank.
The book specifies 35 ft-lb for the bolts holding the side plate, so I torqued them to 35, and one of the bolts snapped, while I could feel another stretching. Fortunately, I was able to remove the broken bolt without difficulty. However, I was bugged by this, for I then realized that the soft bolts used were only good for around 24 ft-lb.
The head had a huge amount of carbon, but I don't believe it was ever removed for cleaning.
It polished up nicely.
The new piston and valves.
The engine started right up, and ran well. It has 6 hours on it now, and appears to be breaking in properly.
The entire job took about 24 hours from first removing the hood of the tractor, to reinstalling it.
The original connecting rod. It was good enough to re-use, but a new one came with the rebuild kit.
The original valves. Some erosion can be seen on the exhaust valve stem, but otherwise they were in good condition.