Agree with Walt. Another thing that should be chkd ASAP on that engine is the possible presence of raw fuel mixed in with the crankcase oil. If so, DON'T run that engine until the oil and oil filter have been changed out. Crankcase Oil diluted with gasoline leaking in thru the carb (usually due to a float needle valve not seated) will not provide adequate lubrication and can lead quickly to total engine failure.

OK, you guys were right. I did have two seperate problems. When I went to cut my grass on Thursday, the motor was "hard starting" again. During the initial crank it did stop turning, which I suspect was that "stop on compression" you guys mentioned. It eventually started and I cut my grass and confirmed that my previous gas tank venting problem has been resolved. Later, I checked my valve gaps and they were not too far out but I am not sure what constitutes far out. First, I did Walt's test and confirmed that the intake valve seems to do a small movement after it closes that I believe is the compression release. I checked this before and after I adjusted the valves. When I first checked my intake valve clearance, at first I couldn't seem to even push a 0.005" feeler through the gap. Then when I played with the rocker arm it went though no problem. An 0.008" was very snug. So I took that as out of spec. for the 0.003"-0.005" it should be. Now, even with me playing with the rocker arm a 0.004" will go through but the 0.005" will not. On the exhaust side, when playing with the rocker arm, a 0.006" will snuggly go through but an 0.008" will not (I don't have a 0.007"). So I took that as OK for the 0.005" to 0.007" spec. and never changed it. When I was done the motor started up very well but I had that happen last week when the motor only sat one day, so next week I will be able to test for sure. It seemed to be more hardstarting when it sat for more then 5 days. Since I like to understand these things, I have a few questions that maybe someone could help me with: 1) Since the intake valve seems to control the compression release, how important is the exhaust valve clearance? 2) Does this compression release keep happening when the motor is running or just during start up? Seems that you would like it during start up and hate it during running. 3) If the valve gaps were to wide why would my motor seem to only have hard starting issues during initial start up but when warm it seem to start up just fine? Thanks for your help.

Given your description, it is possible that a big chunk of head gasket blew causing at least a no compression feeling . I had one a short time ago that blew about an inch out and made only 25 on the gauge. More commonly, the head has let a valve seat slip out of place and it is holding a valve open. Do this. Remove the spark plug, take something similar to a small wood dowel and turn the engine screen on top by hand to see if the piston is travelling. If it is, off the rocker cover comes and if there is nothing visibly wrong there- off the head will need to come. As a hint, with both push rods removed, the ends of the valve stems will protrude from the head relatively equal. If not, something is holding a valve open such as a seat that has dislodged or a screw, piece of debris etc. Using that same logic, it is a good time to verify that both guides are protruding about the same distance from the head as well.

Thank you for including your "start up procedure" in your post. Good detail! But I still need to ask: Does the "backfire" sound like a loud blast from the muffler? or is it a more subdued noise like a loud "cough" back through the air intake components? And does the noise occur INSTEAD of the engine starting up (when you first turn the key) or does the noise occur after the engine starts........and when you remove the choke? If the backfire occurs when you remove the choke, you need to try removing the choke gradually over a period of about 15 or 20 seconds instead of removing it in one rapid stroke. Cold engines need a very rich fuel mix in order to get started. The choke accomplishes this by depriving the engine of most of the air wanting to rush into the intake when the engine begins turning. Because the choke is blocking the air flow, the mixture of fuel & air entering the engine is at this point "mostly fuel"....and that is what the cold combustion chamber needs to sustain combustion. Removing the choke before the combustion chamber has warmed (and it warms up in about 30 seconds) enough to sustain the combustion process can cause the mix to become very lean because there is a slight delay in the fuel flow out of the carb increasing to match the increased air flow when the choke is thrown open suddenly. Unless the engine is showing a lot of power loss under heavy load conditions, there is no reason to think this might be due to the carburetor needing to be cleaned or other reasons. Try gradually removing the choke and see if the engine behaves.