What am I missing - smoking lawn mower content

I have a John Deere L120 from like 20 years ago. It has a Briggs and Stratton v-twin Intek 20 hp engine. As of late last summer it will start with a cough of oil smoke and then run with increasing amounts of gray smoke from the exhaust area until it loses power and dies.

I should note first that I cannot say with certainty that the one symptom is connected to the other, and that that assumption may be clouding my brain. 
 

It has 110 and 150 compression, a single exhaust exit, pulling spark from either side does not seem to affect the smoke output. The spark plugs don't look oily to me.

The actual exhaust tip is hidden from me so I cannot definitively say the smoke is coming from the pipe itself rather than the copious amounts of oil that seep from the engine dripping onto it while hot. 

It didn't die while sitting there running at full throttle for ten minutes but did and does die after 5 minutes when I drove it around, mowing. I can see fuel in the filter after it dies.

It will not restart after it dies until it's cooled off. The actual dying is a noticeable loss in power followed by stuttering and dying. 

I've had another mower with a bad gas cap that would vapor lock so I tested it today by leaving the cap mostly off and it still died. 

When I turned it off today while testing for ten minutes at full throttle (not driving) and the front cover up, it dieseled back to life momentarily and sputtered smoke from the intake. 
 

It's not overfilled with oil. These things are supposedly known for blowing head gaskets.

Thoughts???

Is the choke not fully opening after it starts? Maybe it's not oil smoke, it could just be running rich. My Kawasaki V-Twin mower did that to me once.

It has a separate choke adjustment and once I start it and move the lever it works better when I open the choke. I can mess with it but it's also not black smoke, so I'm doubtful that's it. 

I have a 1 cylinder / 18.5 HP Briggs & Stratton Intek on mine. I think they're a pretty similar design, obviously yours is a 2 cylinder.  I've had two things that caused stall / no restarts over the years.  Lots of videos out there to help diagnose these engines: 

The first was the solenoid on the bottom of the carb bowl got weak and would allow the fuel needle to close when it got hot.  If you see a wire going to a metal donut on the bottom of the carb you have one.  Fairly cheap part and pretty quick fix.  It's there to shut the fuel off when the engine is shut off and it's common for these solenoids to fail when hot. A second failure mode is to fail open and fill the engine with fuel causing a hydrolock condition.

The second was too much clearance on the valves when hot, I remember the spec being .005-.007 and mine being around .009.  I reset them and everything was back to normal, I remember that being at around 450 hours, now at 648 as of this weekend and going strong.

Fuel, spark, compression.  When it dies, check hot compression right away.  When they get older stuff tends to leak more.  My old snapper would run great as long as it ran.  After a half hour if I turned it off it would not restart until cold.  If compression is good, check for spark.  If both these pass, squirt some ether in and see if it works.  

My money would be on a worn out motor.  110 PSI is low, when it gets below 100 starting can get tougher.  At 90 it is toast.  

So glad I have an electric mower, and time to walk behind it now.

I've had a similar problem with losing power and ultimately stopping and not restarting until cold with my Briggs Vanguard twin.  It was caused by a mouse nest between the sheet metal shielding and the cylinders causing lack of cooling and overheating.  A few cycles of that and the rings and bores were bad, so I replaced the bottom end.

I have a John Deere mower with a liquid cooled Kawasaki so I'm not sure how relevant my experience is. What I've discovered is my engine will behave very similar to yours when the air filter is dirty. I missed the issue when it first started happening as the filter looked fine to me but a new filter fixed it like magic.

Help me with the fuel filter picture.  It looks like the gas level is at the green line.  You'll never get all the air out, but it should be more like the purple line.  If I'm seeing that correctly, you have a  fuel issue.

The smoking is just a thing.  Might have worn or cracked rings.  My Kohler burns a lot of oil at startup and then tapers off.  Unless it's causing massive smoke billows that make the neighbors complain, just keep adding oil.

Curtis73 (Forum Supporter) said:

Help me with the fuel filter picture.  It looks like the gas level is at the green line.  You'll never get all the air out, but it should be more like the purple line.  If I'm seeing that correctly, you have a  fuel issue.

Yeah, I'll look at it when it does start and see if there's anything different happening. I really do wonder if I have two separate issues. 

I have a Troy-Bilt LTX1842 with the single cylinder Intek. It has the annoying carb fuel bowl solenoid thing too. I thought the thing was dead last season because it was surging and blowing ALL the smoke and generally exhibiting the same symptoms. Turns out that I forgot to shut the fuel valve off when I stored it and fuel got into the crankcase because of that solenoid. I drained the oil, changed out the plug, tossed it back together, and it ran great for the rest of the year. 

They are also notorious for blowing head gaskets, so it could be that too. 

I had a Honda that behaved similarly and finally just quit. 

It had a stuck valve and was running crappy because of the poor compression.

Might be worth popping off the valve covers and taking a look.