Could be a loose Intake Valve Seat although I would not think the compression would be that good. Seat MAY just be coming loose when engine is hot, operating temp.

Walt Conner

I thought I would run it for awhile and after it warms up, quickly remove the valve cover and check the valve clearances at TDC + 1/4" and see how they change.
Maybe at the same time I can rotate the flywheel and make sure the valves DO seat well.
Another observation I can add is that when I ran it last night cold I noticed that the carb intake felt smooth with most of the air movement sucking in and would easlily pull against you palm. After its hot the intake seemd to become more of an exhaust, louder, popping and pushing air out forcefully.
Rob

***"Could be a loose Intake Valve Seat although I would not think the compression would be that good. Seat MAY just be coming loose when engine is hot, operating temp."***
Very good posibility, based on the saga so far. What might be happening too, is the possibility that the intake valve stem itself may be slightly "bent" by now if the valve seat has been coming "out of pocket". If the valve stem is slightly bent, it could make the valve "slow" to seat at higher RPM (because it is trying to stick, in the valve guide). Is 31H777 an OHV or a flathead engine?? I can't get a Briggs IPL without the type number.

It is an OHV engine.
Here is the full model, type and code:
31H777 / 0235E1 / 040109ZE
If I removed the intake valve could I tell if it was bent or if was sticking in the guide?

IF, you remove the intake valve spring and the valve guide seal, you will be able to tell if the valve is "sticking" by how freely the valve moves the entire length of the valve guide. The valve should be free enough "fall out" if the head is turned upside down (valve face is pointing toward the ground). Before you take the head off and disassemble it, you might want to do a poor man's cylinder leakdown test using compressed air to find out where you are losing compression. Do you have a sorce of compressed air?

Here is a link that might be useful: 31H777 IPL

I have the air, not faniliar with a leak don test?

A "cylinder leak down" test (or reasonable facsimile) using compressed air can be done to identify the route by which the compression is escaping. To do a "bona fide" leak down test requires a "percent of leakage gauge". A close approximation of the test can still be done if you have (1)Compressed air available, and (2) a threaded adapter fitting that will screw into the spark plug hole and also receive an air hose, (3) a means of securely locking the crankshaft/flywheel in the "TDC of compression stroke" for the cylinder to be tested. Locking or holding the engine from turning when compressed air is applied to the cylinder is very important, both for personal safety, and, for accurate test results!! Actual testing is simple and amounts to listening to determine where the air is escaping when compressed air is applied to the cylinder through the spark plug hole adapter fitting. As follows: Turn the crankshaft/flywheel to position the piston of the testable cylinder to TDC of the compression stroke. Here's a hint, the valve train for both valves of that cylinder will place the valves in the closed position. you determine this by watching the tappets through the open valve compartment (if applicable) or by watching the valves with the valve cover removed. When both TAPPETS or lifters, are retracted toward the camshaft, and you can detect clearance between the end of valve and the tappet.....lock the flywheel in place so the crankshaft can't turn when air pressure is applied to the cylinder. Failure to securely lock the flywheel against moving could result in personal injury if the crankshaft rotates in reaction to the compressed air applied to the cylinder. In addition to the locking of flywheel, keep your hands away from the flywheel and crankshaft until air pressure is disconnected from cylinder. With the flywheel locked securely, thread the adapter fitting into the spark plug hole (threads are 14mm dia. X 1.25 pitch when you ask for the adapter fitting) and tighten it so it can't leak air. Connect the air hose from a source of compressed air (60psi to 90 psi recommended). IF, there is a loss of compression, you will hear air leaking from somewhere. Carefully determine where the air is escaping by using a 2 foot length of hose or tubing. Place one end of the hose or tube close to an ear (but not inside your ear) and then move the other end of hose to the exit portal of the exhaust system. If air is heard loudly escaping here, the defect is in the exhaust valve or seat. Check the intake valve condition by moving the end of the hose to the throat of the carb (throttle must be held wide open, choke butterfly open, and any crankcase breather hose must be disconnected from the carb, if carb is mounted to the intake manifold). If air is heard loudly here, the defect is in the intake valve or seat. If you do not detect air escaping from either of those places, check to see if you can hear air escaping from the crankcase breather hose (or pulse hose if impulse fuel pump is present). If you hear air escaping from the crankcase breather hose, or pulse hose, the defect is in the piston or cylinder wall. Always remove the compressed air supply from the cylinder before unlocking the flywheel. A leaking head gasket serious enough to cause loss of compression would be obvious without any test equipment, and you know it right away when the engine is running.

Thanks for the instructions,
I just completed the leak test, and with the cylinder at TDC (with both valves fully closed and clearance at the end of the valves) there is air leaking by the intake valve and blowing into the carburator.....
Guess this is the problem.
The valve seems pretty clean and straight as far as I can tell. It moves in & out of the guide easy, although I havent removed the seal yet (afraid Ill break it) and the valve seat on the head looks clear but with a little gunky stuff around the edges. It appears to seat ok to the eye but obviously the leak test shows its not sealing.
I am considering cleaning and polishing everything good and putting it back together for a quick test, If the head gasket will hold. Im guessing that the valve must be bent or warped and when it gets hot the problem shows more.
Any chance I can polish the fit myself and not have to buy a new valve?
Will the head need to be re-ground where the valve seats?

Being too impatient to wait for a new valve to arrive I decided to try to make this one work. I used a wire wheel to clean up both valves and the head. I then put some blue dykem on the intake valve and seat and used some 600 grit polishing compound to see if I could see where it was leaking. I quickly polished a perfectly smooth and even ring around the end of the valve and it looks great. Seems airtight until I do the leak test and air still gets by the valve and blows out the intake, not a lot but a steady hiss.
I guess if this is supposed to be airtight I will order a new intake valve.
Even though it has only been ran about 30 minutes since I replaced the head gasket, I noticed that the head has warped a little again. I had ground it perfectly smooth before and now the area around the center is about .001 to .002" lower than the outer edge (where all the bolts are). I noticed that the exhaust valve only moves about 1/3 the distance the intake valve moves. Is this normal? I checked to make sure the muffler was clear but perhaps I have a backpressure problem by not exhausting enough air?
Going crazy here..

Mine had similar problem last year. I spent an entire morning checking stuff out, including using a spark tester tool, checking the valve clearances and the 'coil'. Anyway, none of those were the issue, the issue was that the carburetor choke was NOT spring back to the 'open' position after engine warm up/engine start. I saw some 'fixes' on the Internet which detailed how to remove the verical carb butterfly shaft and shave it down a little so it wouldn't stick. I figured I could always 'open' it manually with my hand after a few minutes, but instead drilled a small hole forward of it in the plastic housing, and put a 25 cent spring from there to the ALREADY-PRESENT hole in the black horizontal lever that attaches to the vertical butterfly shaft. See photo at http://www.uploadhouse.com/viewfile.php?id=2339206 before I added the spring. The hole I used is in the foreground; the choke lever from the driver seat pushes the black lever counterclockwise to close the choke, and when I release that lever, the spring I added pulls the black lever clockwise to open the choke.

Huh! I guess I fell for that ploy. It seems that when you click the link, you get a photo of cusser wearing a pair of "granny panties" in addition to the choke hold. Cheap trick :^)