***"I see a couple embers (for a lack of a better word) coming from the muffler"*** I don't think you can use a better word to describe the...uh..embers. That is exactly what they are. These embers indicate a fairly heavy build up of "oily soot" (carbon) in the muffler and exhaust passages from the "oil burning" you stated. Worse (maybe) is the probability of the combustion chamber (piston crown, cylinder head, and the "uncovered" upper margin of the cylinder) being covered with this junk too. If this a very old engine ('71 model, still under warranty, right?), the intake manifold passages and intake valve probably have their fair share of buildup too. Interesting point you made about the embers. I will guess (or bet) that the engine is "tossing embers" occasionally all the while you are operating it, not just at "shut down"! It may be that the embers are just more noticable in the darker inside where you park it. If you ran it outside at night, you would probably see embers out in the open. Run it outside about 3:00 AM and maybe a neighbor will put it out of its misery. :^) Seriously though, the carbon build up inside the combustion chamber could be a factor in your loss of power. When a combustion chamber becomes coated with heavy carbon build up, these deposits can develop "glowing embers" or "hot spots" that can be an "auxiliary source of ignition" causing the intake fuel/air charge to "pre-ignite" which will result in a net loss of power from the engine. As the temperature of the combustion chamber continues to rise, more "embers" will develop until soon, you have nothing but "pre-ignition" and spark ignition takes place as "an afterthought". I presume that this old Kohler engine would normally "shut down" by killing the spark and denying the engine its source of ignition to "light the fire" in the cylinder. You state that it "does not shut down as smooth as normal. Never was great, though. Both times shutting it down, right at the end, it sputters". I believe that the embers in the combustion chamber are continuing to provide ignition (and these old carbs keep on providing fuel as long as the engine is spinning) after you "kill the spark plug" and that is why your shut down is "ragged, prolonged, and sputtering" (complete with fireworks). "Is the poor motor finally giving up?" It certainly appears to have reached a "plateau" in its life. You could probably rebuild the engine (if parts are available) and get another life cycle out of it. It will require a complete disassembly, clean up, and inspection, including "miking" all the components to see if they can be reused, and whether the cylinder would need to be "over bored" (with a larger piston to replace the obviously worn out, old piston). Could be pretty expensive if it's done right. Be a lot cheaper if you can do the lion's share of the grunt work (R&R and disassemble engine and reassemble engine). If you can't perform most of the neccessary work, you'll probably be better off finding a replacement engine to go in. If this sounds like "too much" to sink into a 1971 tractor (even though you've had it how long?), you might as well start hunting for a replacement tractor.

***"I doubt a "defective air filter" is the cause of a wasted cam lobe on your machine. #2) I doubt the air filter has caused *only one* of your cylinders to give up the ghost either."*** I agree with that. When the air filtration is not keeping dust and grit out of the engine, the first components to suffer are the intake valves and piston & rings/cylinder walls. Secondary components to fail would be camshaft lobes, crankshaft rod journals and piston wrist pins. If you don't "see" any visible signs of filter leakage (obvious "dust tracks" or "dust streaks" showing in the areas "past the filter", dirt in the carb throat and intake manifold (some traces of "carbon black" in the intake is OK. Dirt, grit or "sludge" is not OK), about the only way to confirm the presence of inadequate filtration, is by doing "autopsy" to the disassembled engine and components. In an "autopsy", all engine components are measured with precision instruments (micrometers, dial indicators, "plastigage" to name some)and compared to the OEM specifications and/or wear limits. The two "most telling" things to measure when you suspect that air filtration has been "compromised" or "corrupted", are the diameter of the piston "skirt", and the diameter and taper of the cylinder walls. In measuring a piston, you DO NOT measure diameter anywhere in the piston ring area. The measurements are taken across the "skirt". The "skirt" of the piston is the "long, round surface of the piston sides". The skirt is the portion of a piston that actually "supports", or "carries" the side loading of the piston that occurs when the rod journals of the crankshaft are "half way between TDC & BDC" of piston travel. For this reason, the cylinder walls will wear where the skirt "rides" more than other areas. In most engines, you will be able to actually see the "track" where the piston skirt "touches" the cylinder walls. This track is where you want to measure the cylinder to determine how much it has worn. Measure the cylinder walls that are "perpendicular" to the skirt track AT THE BOTTOM OF THE CYLINDER. This point of the cylinder will give the original diameter of the cylinder when the piston was "put into service". Knowing the "new" measurement allows you to subtract that value from the measurement taken in the skirt track of the cylinder. The "remainder" from that computaion represents the amount of wear that has occurred to the cylinder. In measuring a piston, you take the diameter spec for a new piston and subtract the measurement from the worn piston. The remainder from that computation represents the amount of wear that has occurred to the piston. You can then compare all your measurement results to see if the engine would require "over boring" the cylinder to the next appropriate "oversize" of piston. Over boring a cylinder requires an oversize piston. And, you can't use an oversize piston unless you also over bore the cylinder (they only go as a "pair") If the engine features "cast iron" liners, and dirt and grit are getting into the engine, the wear to the cylinder walls will be worse than the wear to the piston. This is because the "softer" aluminum of the piston allows some of the grit to "embed" in it. The embedded grit acts like "emery" and will cut into the cast iron while the piston itself gets "less wear". Aluminum cylinders & pistons will wear about equally. Anyhow, if the cylinder walls and piston skirt exhibit "excessive wear", the wear is most likely due to bad air filtration. So, if you think you might want to "save" this engine by replacing the camshaft (which is obviously worn), you need to perform (or have it done by a "machine shop") an autopsy to determine if the engine is a candidate in the first place, and if unfiltered air was the cause. With today's costs of machine shop operations plus the high relative costs of individual replacement parts, you have to decide whether to save that engine, or replace the engine. If all other parts measure within acceptable specs, a replacement camshaft kit is likely a good way to go (even better if you can DIY). If the pistons and cylinders (even one piston and cylinder) are worn beyond the service limits, a complete new engine makes more sense. BTW, the 120 PSI versus 135 PSI on the "good" cylinder probably reflects the worn cam lobe more than the leaking head gasket.

rob, The camshaft did not wear because of the valves being out of adjustment. Valves being out of adjustment will not create high compression. The camshaft is not sensitive to compression in the cylinder at all. The ONLY pressure, or loading, on the camshaft, is due solely to the pressure of the valve springs. There are no other forces or phenomenons working against the camshaft. As to not exhausting enough gas, cycle of quick wear, higher pressures that even warped my head. None of that has happened to your engine. Those things simply do not take place. Sorry. The camshaft is worn out, most likely because of poor quality control during the finishing and hardening phases of manufacturing the cam. The camshaft ended up too soft as a result. Other factors might contribute to warping the head. If you have never removed the sheet metal to check your cooling fins for blockage, that might be a reason the head gaskets blow and the head warp. The other aspects of your thread are something only you can decide (fix, replace with same, replace with different).

I would pull the plugs and read them. spray some carb. cleaner down the spark plug holes and motor the engine over (motoring the engine would be with the spark plugs removed turn the key and let the motor free spin blowing out the carb. cleaner and anything else) If the plug were good I would clean and regap them before I installed them. If one was black sotie and you have no ignition problems as suggested above I would do compression check. If you have at least 100 psi in each cylinder I would suspect dirty carb. and fuel system. If the compression was low in one or both cylinders say 60 psi or lower then you would have to get pass that problem before continueing of course.? I would then do a fuel system clean up if the compression is A OK!. (probably needs it anyway and it don't cost you nothing but time). Fuel system clean of consists of replacing the fuel filter, inspecting and blowing out the fuel hoses (all of them including all the way to the tank), remove the gas tank clean it out with bottle brush type brush by scrubbing the bottom and sides or using a pressure washer and rinse with fresh gas, last would be removing the carb., disassemble and cleaning of all the small passages. When you inspect the fuel lines any weather cracks or dry rot I would replace them. I replace them anyway while I have it torn apart cause you really can tell the condition internally of old 10 year old fuel hoses? I have found if I do my part my vanguard will almost out live me! time will tell, I'm 58 and the vanguard is 21!?!