I was having a little trouble getting the rings into the cylinders on my 836 refurb, so I decided I needed ring compressors. I had an old rusty 836 sleeve that I had practiced using the hone on so it was now smooth, and a little oversize, I cut a couple slices out of it, split them in half and smoothed the edges.
They fit perfectly over the 836 pistons and with a hose clamp, the pieces perfectly pushed the rings in. I adjusted the tension so the cylinder could slip right down over the piston/ring assembly. It worked like a champ.
And then I loosened the hose clamp, you can see where this is going. The back half of the ring compressor is now able to free fall into the engine. And yes, it did. A piece of slotted cardboard under the piston or even a rag over the case opening would have cured the problem. I pulled the cylinder off and tried magnet fishing with no good result. Luckily the ring compressor landed near the oil pump and I still have the pan off, so I fished it out of the bottom.
4 hours later, I'm back where I started. Cylinder off again and drinking beer.