Perculiar lawn mower problem

I have a Sears lawn mower, rear drive, 6.5 Hp Briggs and Stratton engine that is five years old. It didn't get much use when we got it in the fall five years ago, and then the following years we had somebody mow our lawn so it sat for four years. This spring I fired it up and it ran well until the last few times. The symptoms are this:
Takes several tries to get started. Prime the bulb and pull cord, will run for 5 seconds and stop. Repeat this five or so times until it stays running.
Then will run for 20 or so minutes and then run erratically and stall After stalling, the engine must be bulb primed to get started again. Will run for a minute and then stall again. Repeats this over and over until I give up.
Before I bring this in to get serviced, can I get an idea what might be causing this. I'm wondering if it's worth the repair bill.
Thanks for your replies.
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fall
so
the
run
After
for
up.
Carburetion/ fuel system (from sitting)

Only you can answer this.
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Would that mean a nwe carb? What exactly would cause it to have problems at startup and after running 20 minutes? I assume heat is an issue, but how?

I'll have to research the price of a carb. I could probably do it myself.
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I never met a carbuerator you couldn't clean. Some of my equipment is 30, 40 & 50 years old - and I've never bought a new carbureator. The closest I came was a rebuilt carb on a 1940's Jeep.
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engine
lawn
run
at
I'd look at fuel delivery first. Check the screen in the tank and the gas cap (vent). It sounds (to me) like the flow of fuel is restricted. I've seen the cap vent cause this problem. After that checks out I'd look at the carb. Pull it, disassemble, clean, adjust, re-install. I bet you'll find some crud in the passages and restrictions in the fuel supply.

You might be able to get an estimate to better help you decide.
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What would be reasonable to clean it with? Rag, solvent, WD40?

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gas
Go to the Auto Parts Store and get some "Gum Out" or similar carb cleaning solvent. Wear eye protection and use in a well ventilated area (that stuff is nasty). Use a toothbrush and fine wire to clean all the passages. Blow out with air, re-assemble exactly in the reverse sequence from the way you took it apart. I usually work on a clean towel so I can see all the parts if they drop.
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Thanks. It's been almost twenty years since I worked on cars and I've lost my memory of how to do repair engines.
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I've
the
some
cleaning
stuff
Blow
you
parts
lost
I too suffer from CRS (Can't Remember Shit). Just take it slow, make notes of the sequential steps (if you need to). Clean each part and lay it out in order. They've not changed a lot in 20 years. You don't get extra points for leftover parts. :-)
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fr0g wrote:

Hi...
I guess I have it too... darn! - forgot what I was going to say :)
Ahhh, got it. Virtually everyone these days has a digital camera, or at least one available to borrow. Pics are free with them, so as you dissasemble take lots and lots of pictures of everything from every angle.
Makes it much much easier to put things back together correctly :)
Take care.
Ken
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FDR wrote:

If you don't know what to clean a carburetor with, I wouldn't suggest taking the carb apart. Spend the $50 or $60 and find a reliable small motor repair shop. I paid $70 to have my garden tractor's carb cleaned. It would have been much cheaper if I could have delivered the mower to the shop myself. As it was, the bill included pick up and delivery of the tractor.

--
Bill
In Hamptonburgh, NY
  Click to see the full signature.
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My guess is your mower is overheating. Are there leaves and grass clippings clogging the cooling fins?
FDR wrote:

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No, doesn't look it.

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Overheating after five seconds ???
Come onnnnnnnnnnnnnn !!!
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FDR wrote:

You didn't mentioned whether or not you prepared the engine for storage 4 years ago before you let it sit unused for 4 years. Did you completely drain out the gasoline and run the engine until it stalled from lack of gas? Gas goes "stale" after a few months and can create "varnish" deposits in the carburetor which interfere with proper carburetion.
If you're not mechanically inclined, and aren't prepared to disassemble the carburetor, then you might try this first: If you haven't already done so, completely drain the old stale gas out of the tank, and fill with fresh gas. Then go to WalMart and buy a bottle of Chevron Techron. Put a couple of ounces in the gas tank and run the engine for 5 minutes. Then shut it off and let the mower sit for 24 hours. Then start the engine again and let run for 5 minutes. Repeat this for a week or until the problem clears up.
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It was free of gas when I stored it. It ran well for the first four or five times I had it out of storage, just stated going bad recently.
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These guys sometimes have a fuel pump in the carb that runs on vaccum. If so, the diaphram can be replaced. I have had problems with ethanol in the gas. Make sure the fuel flows freely from the gas tank. If not, the fuel line and float bowl will be full initially but the fuel flow won't keep up with the usage. In about 20 min. the engine will starve for fuel.
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