Outdoor Power Equipment and Small Engines - Stuck valve on Briggs 5HP, how to remove?

I have an early 80's Troy-Bilt Pony tiller with a 5 hp Briggs, horizontal shaft. I stupidly used it for a while with VERY lousy gas in it. It ran OK but you could tell the gas was poor. The other day I took it out and it bumped coming down a step from the shed. Since then, it has no compression.

I pulled the head and there was a lot of carbon buildup and the intake valve is stuck open. I sprayed carb cleaner and some PB blaster into the opening under the valve, and if I let it sit for a few minutes, it will come down on its own. When I turn the flywheel it pops back up but doesn't come down. I assume some carbon buildup went down into the stem or springs when I bumped it.

What should I do? I'm not sure how to remove the valve. Any suggestions?

Thanks!!!

Get some good carb spray, remove the head again, rotate the engine until the valve is up. Spray the stem a lot, and spin the valve with your hand, to get some of that carb spray down in the guide to dissolve the gas varnish.
Rotate the engine some more and push the valve down.
Keep doing this until it is fixed. Change the oil as the spray will have fouled the oil, put in fresh gas, and run it.

Fish

If you get to the point of removing the cylinder head (and I agree you should) then instead of hoping spray cleaner disolves the carbon (which I doubt it will) then you should remove the breather assembly, next, so as to remove each valve and clean and polish each valve stem and find something suitable to clean and polish each valve guide. Be sure to also clean any and all carbon deposits from the entire combustion chamber and remove all signs of old head gasket material on both the deck and cylinder head. You'll need to purchase a new head gasket and a new breather gasket and possibly, depending on your Briggs model, type and code, new intake and exhaust gaskets.

Will do. On turning the valve--how easily should it turn? If it's very difficult, is there something else wrong?

The valve will turn easier after the carb spray gets to the varnish on the stem. Just make sure the engine is holding the valve up when you are turning it, or it could snap and pinch your fingers.

Well, it was much better last night. The valve returns on its own as I turn the flywheel, but it still might be just a little slower than it should be. I gave it another round of carb cleaner and turned the valve as I did it. It was pretty difficult to turn but it didn't bind at all. I'll keep at it. Thanks for your help!

As for the head gasket, I assume I should get a new one--does anyone know where I can just get the gasket without springing for a whole rebuild kit? Is it ok to reuse the old head bolts? Torque?