I have had one mower and one weedeater in my life that lost compression. With a pull start you will know right away. Electric start you may not. Even though the mower had lost nearly all compression it would still start and run for about 2 minutes though.

For what it is worth.

I checked my 17.5 Briggs today. I pressed on the flywheel screen and rotated engine by hand. The compression stroke was obviously more difficult to to pass top dead center. I forgot I have compression gauge. But, I expect we could find that number on the net.

Willhunt, any luck on your situation?

Lazyjack, no sir not at this time, this is a deer lease mower and have not been out there in a week or so, Will check compression for sure. Cannot help but think fuel even though the spark plug was wet. If I am not mistaken it was running well slowly lost power, then stopped. Will keep you posted on the outcome.

I tried the same thing on Wilhunt’s mower the other day and could not turn flywheel past tdc by hand.

If it won’t rotate by hand something is likely out of wack bad or the float is stuck and the cylinder is full of gas.

If full of gas you likely need to drain fuel and change oil.

The easiest way to diagnose this is still a compression test, especially if it's a single cylinder engine (can't see where that was answered). Flat cams are diagnosed most easily with a compression test too. That's why it's pretty silly a shop teacher would put fuel and air together as fuel. A bad carb, a vacuum leak, a bad intake cam lobe, or restricted exhaust all cause AIR problems, not fuel problems although a flat cam lobe would also fall under the compression umbrella of the big FOUR and carb could be either air or fuel. ASSuming an engine has compression is dicey at best. It most fits the symptoms here so that would be the logical test procedure. This topic and the one about the truck that died after running out of fuel are pretty funny as people guess what part to replace without any diagnosis.

On a side note, we have the ability to compression test without pulling a spark plug. A laptop, an application, and a scope with leads tells us if a cylinder is down by measuring the electrical load as the engine turns. Won't tell us which cylinder because the app doesn't have a reference but that's okay because we can tell which cylinder by the scanner data. Helpful on multi-cylinder engine WE KNOW are misfiring on a particular cylinder but need to know which of the FOUR that cylinder is missing.

Well it was a text book that put them together. Air is also fuel so doesn’t seem odd at all they would be put together. Ain’t burning much without oxygen.

You really type some of the oddest mechanical posts ever. Air is not fuel. Fuel is fuel and air is air. They are two of the four things a gasoline engine needs. Can't put only air or only fuel in and expect it to run. So no, fuel and air are not the same. If so, we could avoid the FUEL stations altogether because there is plenty of air. A lot of hot air in here.

Nitro and diesels engines are throttled with fuel not air. Boom. Some minds blown.

He is out of his depth quite frequently. He doesn't know it, knows it and doesn't care, or is too dumb to know the difference.

Says the short guy.

You burn the gas with no air I want to see.

My point exactly. Takes fuel and air. Those are two things you counted as one.

Guys…once ya’ll finally agree, if ever, on this, will it have helped the OP. Silly argument…

Hopefully the compression test has been done by now. I’m guessing that it has compression, or enough. So, it has spark, air, gas, and compression. I still think the issues is in the carb - getting bad fuel delivery.

And please do clean the spark plug.

I forgot you were the other person that said a gas engine needs three things to run.

You really can’t let go of that, can you? Of course it needs compression, but in a machine recently run by me, I usually assume it still has enough to run. I’ve run quite a few old machines that had very little compression but still ran - sort of, and weakly.

Now…assuming there is enough compression, how many of those other things do you need to have? Is it 3? Come on, say it, it’s 3 isn’t it.

I said air was part of fuel. An air fuel mixture. I mean how petty do you want to be? I mean even with air fuel fire and compression it won’t run if the timing isn’t correct. This is dumb.

We’ve beaten this to death. I really would like to find out what the problem really is or was.

you guy's are silly, the 3 are, fuel, spark, and compression, as the old saying goes. nerds

No air?

You left out TIMING. It's five.

Nice but that falls under spark.

and air induction falls under the rotating assembly, the intake stroke

Rotating assembly is not one of the four things a gas engine needs to run.

To some, the desperate need to argue with someone will always be paramount.

Your right, it could have sheared the fly wheel key. My 42 inch is a kidney buster.