This is a 'real' Lawn-Boy with a somewhat complicated engine-management/governor system rather than the simple air vane/spring system of the later models. I haven't worked on one like that but there are a number of adjustments/parts that control engine speed. So I'll defer to others, like 'Walt' who has experience with them. But, there are still some things to check. The first thing is it is entirely possible that with the age of the mower and the fact that you have used it without an air filter element that it has lost adequate compression to develop power. Another common problem on old LBs is hard carbon build-up in the exhaust ports and muffler assembly. Assuming you used the right crankshaft seals and installed them correctly, and they haven't blown out of position, that factor should be okay. Contamination in the carb from lack of air filter could be another. The ignition coils have two-phase operation, where the 'start' phase works up to 800 RPM, then the 'run' phase takes over. If the 'run' phase in your coil is not working, it would act like you describe. That's about all I have. Hope you can solve it.

***"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.

Thanks Mikie, You give me too much credit for computer knowledge: I do not know what "the Modern Screen" is ... ever notice (may be a statement on my failing old man vision) how much "rn" and "m" look alike? Well on my font and size, which is the default on comphelp dialog. I have not seen the subject problem repeated. But the slow responses to my keying in still goes on for several minutes after a boot up, again several times a day. Suppose it is Avira or some other "good thing" the CUP is really pumping on some task.

Most likly a shorted horizontal output transistor. It will be the largest transistor, located close to the high voltage transformer. This can be tested "in-circuit". With an "ohm meter", measure between "base" to "collector". With the meter probes placed in one direction, the reading should be infinite, reverse reading should be about 500 ohms. If the transistor is shorted, replace with the same number as printed on the transistor. Resolder the leads on the horz driver transformer, replace the filter capacitor attached to one leg of the horz driver transformer. Use the same size and observe proper polarity. good luck, pw