Almost 2 years ago, I made a plow front-end for my walk-behind 52" hydro mower, and it's worked pretty good for me, except that it doesn't like starting when it's cold out (below about -15C or so). Last year, I upgraded the battery, starter solenoid and wiring to the starter, switched back to the original air filter setup from the remote setup I made for it, and figured out that I need to turn the choke on when I turn the engine off, as some moisture always seems to be in the intake of the carb, and that water will freeze and prevent the choke from fully closing (it's spring loaded going in that direction, but not in the other direction, when I turn the choke off, so I can push it through that little bit of ice).
From an email chat with a Kohler engineer (it's a Kohler CV22S engine), he suggested that getting warm air from around the muffler would help. Other versions of this engine, which have a different air filter/intake setup, Kohler sells a kit for doing this, but they don't make one for my version, as it was meant only for being used in the summer.
So, I made a new air filter housing so I can get warm air from around the muffler:
It's not quite finished yet, as I need to make an end-plate for the heat shield around the muffler, and I've got some stick-on cork material to seal up the joints of the intake a little better, then I'll test it and see if it does make a noticeable different in intake air temps (well, I don't have a remote temp sensor, so I'll just use an IR gun to check if the intake housing gets warmer).
If it doesn't make a difference, I'll try reducing the gap between the heat shield and the muffler.
As for "real" machining content, I tried using my lathe to part of pieces of a muffler pipe adapter (1/2 of it for welding onto the heat shield, 1/2 for the air filter housing). I would get most of the way through, then just as the parting tool would break through, it would catch on the edge of the adapter, and wind up mashing it up into a ball. I'm a slow learner, so I did it twice. Third time, I just clamped it to the edge of a table and used a cutoff wheel on my angle grinder.
I also tried brazing the pieces together (you get see the part I tried, it's the brass-colored bit in the middle of the air cleaner housing). It worked, but not very well, I had trouble getting both pieces to the right temp, and I put WAY to much heat into the top flat plate, warping it pretty badly. I went back to mig welding, and that worked better. It looks terrible (I'm using flux-core), but I'm not burning holes in it like I I was even this spring. Progress!