OK, Dh and I are havig a slight disgreement about the mower. It is a Murray, sold under the Scotts brand in 2000, with a briggs and stratton 6.5 hp engine number 121602.

Now, a cable broke, the one from the handle that kills it when you let go, and it sat outside for a month while we got the cable. REplaced it then the mower would not start. I thought it sounded like it was not getting any gas. It would turn over, but not fire. Now after replacing all the usual (spark plug, oil , air filter) still would not start. Dh finally listens to me and pulls off the fuel line because gas is leaking out the primer bulb. I said, hey, maybe somethig is gunked up because you left it outside for a month? He takes the fuel line there off and pumps the primer bulb to see if it works. After a few tries you can tell something was cleared out of it. You could hear it woosh now. He puts the fuel line back, and starts it up. Now it starts, but it idles at full speed. WAYYYY to fast. Anyway, he spends the day on the phone with his brother, and they go through a lot of things. He took stuff off, put stuff back. I don't know what else. Now it starts just fine, but after about 30 seconds it begins to rev up and down. Almost dying, then going back up. It does not go back up to as fast as it was before though. I say it sounds like something is gunked up in there still.

Anyone have any suggestions? My DH is a wonderful game developeer, but not very mecahnical. My mecahnical expertise is limited to installing light fixtures and building computers! Any ideas would be greatly appreciated.

How old was the fuel that was sitting in it over a month... letting it set with un-stabilized gas (after a month, it starts to go bad without, later on it gets rancid then gummy) And of course if it set in the rain?! It may have water in the carb, and tank...

The reving sounds maybe like a air leak... which can be easily detected by carb or brake cleaner sprayed around the carb seals.

ok, Dh and I are havig a slight disgreement about the mower. It is a Murray, sold under the Scotts brand in 2000, with a briggs and stratton 6.5 hp engine number 121602.

Now, a cable broke, the one from the handle that kills it when you let go, and it sat outside for a month while we got the cable. REplaced it then the mower would not start. I thought it sounded like it was not getting any gas. It would turn over, but not fire. Now after replacing all the usual (spark plug, oil , air filter) still would not start. Dh finally listens to me and pulls off the fuel line because gas is leaking out hte primer bulb. I said, hey, maybe somethig is gunked up because you left it outside for a month? He takes the fuel line there off and pumps the primer bulb to see if it works. After a few tries you can tell something was cleared out of it. You could hear it woosh now. He puts the fuel line back, and starts it up. Now it starts, but it idles at full speed. WAYYYY to fast. Anyway, he spends the day on the phone with his brother, and they go through a lot of things. He took stuff off, put stuff back. I don't know what else. Now it starts just fine, but after about 30 seconds it begins to rev up and down. Almost dying, then going back up. It does not go back up to as fast as it was before though. I say it sounds like something is gunked up in there still.

Anyone have any suggestions? My DH is a wonderful game developeer, but not very mecahnical. My mecahnical expertise is limited to installing light fixtures adn building computers! Any ideas woudl be greatly appreciated.
There are a several possibilities. There could be water in the fuel, a bad diaphragm or a bad spark plug. The fast idle is more than likely caused by the throttle stuck in the wide open position due to being in the elements. Hope this helps.

All Of The Previous Answers Are Good Ones. But It Could Also Be A Malfunctioning Governor (although Not Very Likely), Or Even More Common Could Be The Spring On The Carb Off, Or Set Improperly.
Good Luck.