"I will fill the tank and run it to empty (stalling.)" .... fwiw, I never run equipment where it starves for fuel to stall it out.

Just don't let it run dry and stall ......

 

Yes, perhaps good advice as I will not disagree.
I have no sense of a fuel gauge- either for thyself or on the mower.
I would need to have some sort of make-shift time.

 

Just Might Be Because You Are So High Up There. Might Be Vapor Lock.

 

When you shut the mower off do you hear a percolating sound coming from the carb? As stated could be vapor lock. Try removing the air cleaner and try to start it. I had similar issues turned out to be a clogged air cleaner.

 

I know that it is not the air cleaner since it is new.

Ironically though, a clogged air cleaner is why I have this mower. They guy I got it from gave it to me stating "it ran great until it didn't." I did the typical KISS checklist items and when I checked the air cleaner it was TOTALLY clogged. I put a new one on, changes the oil and sharpen the blade ever once in a while and it has been my go-to mower for the past 8 years or so.

I have heard the term "vapor lock" and understand it better on carburetor automobiles. I recall it perhaps happening on a late 70 Ford. Is vapor lock priarily in the fuel feed line or hose? It appear that ther is a short fule line on the mower in question. I have never changed the fuel hose on it. Perhaps I should go ahead and do that.

 

check the head bolt torque, some times the bolts get loose. Also maybe check valve adjustment.

 

Gotta wonder if the valves are a bit tight, and you are losing compression when hot. Also, I can't remember ever having a mower with a primer at all, much less needing much (if any) choke to restart hot.

 

Have you checked for spark when it's in that hot, no-start condition?

 

I am with the valve adjustment commentators. It was used when you got it and you have worked it hard for eight years, time to check the valves.

 

Valve adjustment, never done it on a mower before but not outside of my mechanical skills.
...need to look at some yootoob videos and maybe see if I can get a copy of a factory manual. Will do some investigating on my lunch break.

 

Bad Coil

 

If it were a bad coil would it not start at all?
It starts fine when cold.

 

Mine was doing that, little by little it got worse, finally it wouldn't fire even on a shot of ether.
It was a bad coil, yours might be on the way out.
Easy fix, not too expensive, just make sure you install it right, has to be about a business card away from the flywheel.
Mine is a Craftsman from 1998, 6.5 horse.

 

another vote for valves needing a tweak

 

Try this. How long does the mower run on a tank of gas say it's 45 minutes. At about a half an hour shut it down and try to restart, if it starts it could be heat related. Just looking for simple things

 

^^--yea, I am going to try that next time I cut.
I was mowing the lawn this weekend over the 3-day holiday weekend between the raindrops and once finished (in a light mist) I just wanted to get inside, shower and get a beer... was in no mood to experiment in the rain..LOL,

 

"...just make sure you install it right, has to be about a business card away from the flywheel. "

Not sure what you mean by that. Can you expand on it?

 

This might not be yours but most lawn mowers are the same principal.
Skip the first part, you still have spark.
Mine went little by little when it got hot it wouldn't start, till it would not start at all.
At time stamp 3:04 he explains the ignition coil, and uses a business card to set it right.
That is what I use.

 

Ah, OK... understand. The business card acts as a feeler gauge of sorts to set the gap.

 

Yes, you don't want it too close and you don't want it too far away.
A business card works fine.

 

Often a sign of a coil on it's way out, will be it will work fine when cold, but once heated up it will not fire.
Next time engine does not start when hot, check for spark. If no spark then the coil is most likely the culprit.
I would check the valve gap also.

 

My first suspicion would be the choke and it's behavior.
is it closing and it shouldn't be? Is it wide open and it needs a little bit of choke to start under these conditions?

I'd pull the air filter off and have a look see and if the choke is open, try covering the air intake with your hand.

 

Plus 2 or 3 for coil going bad. Have a briggs rider that was hard to start hot. New coil solved it.
Also could be overheating/running hot due to clogged air fins.

 

Plus 4 Get a spark tester on it next time it acts up. Easy to verify.

 

Mower: Craftsman 625 with BS engine. Your typical 22", push, high-wheeled push mower. About 20 years old, very good condition. Cutting lawn at 9,500 feet altitude.

I put a new carb on it this spring and still performs strong, but I work it hard in 8-12" cuttings on occasion if I let it grow too long before I can get to it. Kit included new: carburetor, spark plug, air filter.

I will fill the tank and run it to empty (stalling.) This will me give about 60-80 minutes of cutting. I'll take a break, get some water and sit for a while to catch my breath.

After this 20 minute break, I'll come back, fill the tank and attempt to complete the cutting. But the thing will not start! I prime the carb only a few pumps out of fear of flooding. 4 or 5 pulls later I will prime a couple more pumps. No-go so a couple more pumps. At this point I figure the bowl has enough fuel and I prime no more- Yet it will not start!

When it is fully cold (not running at all in the same day), I will give a shot or two of starting spray and it fires up on the first or second pull. I have not used starting fluid in the situation described above in the re-start scenario. I figure it is not cold enough to warrant it.

I must mention that this situation occurred with the old carb as well. I only replaced with the new cheapo $20 dollar carb because it would not start at all when cold.
With this new carb, it is very similar to the old:

• Starts up fine
• Performs (cuts) great
• No start after running dry and refilling

I do mind calling it a day early, but would rather finish the chore in one day's outing rather than needing to finish the next day.

Any ideas or comments?

It definitely sounds like vapor lock to me. I've had several experiences with this. The first was an old Jonsered chain saw that does the same thing as you stated. The fuel is literally evaporating and causing this issue. The old timer at the chain saw sales and repair had told me to always use premium fuel. Well, I hadn't used the saw in quite a few years and took it out to do some work. When I shut it down for a break, it wouldn't start. I went back to the saw shop and low and behold, the old timer was still alive and kicking. I told him what was happening and he asked me if I bought the saw from him. I told him that I did, 17 years ago. He gave me a grumpy old man look (I was 60 at the time, so he had to be damn near 85) amd said - "Didn't I tell you to always use premium gas?" It was that moment that I realized that I forgot what he had told me all those years ago.
So my advice is to dump out your fuel and grab some high octane. I never had any issues after that. Note that the newer equipment runs fine on regular.
I also had a Ski-doo that came with heated carbs (it was the first time they were available and the ran via a water jacket routed through the cooling system) Well, I learned a hard lesson there also. #1, Never use the heated carbs unless it's super cold. #2, turn off the heat and let the carbs cool down before shutting down. Vapor locking an 800cc engine is no fun

 

Vapor locking... the lines or the carb. I think we need to look into a few areas

 

At 9500 elevation with the stock carb,you are running too rich. It is incredible that all of the other responses ignored your elevation. Go to the parts listing for your model and see if Briggs lists a high altitude jet, they do so with many of their motors. If none is listed, give me the letter/number on the bottom of the jet (the nut that holds the carb bowl off the original carb, if you still have it.) If there is a local competent shop, they should know the jet to put in at your elevation. I don't go on this site very often so you can e-mail me at Chipg1956@gmail.com.

 

You mention cutting tall grass often so another thing to look at is blockage of the cooling fins either by mouse activity or grass sucked in through the fan. That would exacerbate any issues the coil would have to heat.