Mower Won't Keep Running

I have a mulching mower that worked fine a month ago. Now, when I start it, it runs for 15-seconds and then quits...unless I push the rubber primer button that puts a shot of gas into the engine. Even after it warms up, it still only runs for 15-seconds, then wants to quit. I hesitate to bring it into a repair shop and pay $75 to fix a mower that's not worth that much.
A year ago, when I brought a relative's mower in that wouldn't start, they cleaned it out and said it was a victon of "old gas"...even though I typically leave gas in my mower and snowblower year round, and they always start.
Any ideas?
Thanks! Scott
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Scott wrote:

Yea, your carb is dirty. Get a carb rebuild kit from the local lawn mower shop and rebuild the carb. Basically you just take it apart, clean it up real good, and put it back together with new gaskets and float/float valve.
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Scott wrote:

Old gas can be a problem, but in general, as long as it is fresh to start with and is kept sealed it should be good for a year. You can buy products to extend the life of gas. Note: if exposed to the air, evaporation of some parts of the gas can make what is left not usable.
I agree with User that the likely problem is the need to clean out the carb.
--
Joseph Meehan

Dia duit
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You have a fuel supply problem.
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Christopher A. Young
Do good work.
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You probably have varnish in the carb which deposited from the gas sitting too long. A higher quality/grade of gas, or the addition of a gas stabilizer like Stabil probably would have prevented it.
Now you'll need to: 1) add a solvent to the gas and run the motor long enough to dissolve the varnish (not easy if the motor won't stay lit), or 2) remove the varnish by soaking the carb in a solvent and scrubbing away the residue, especially in the float bowl and the jets. Most small motor shops will do such a repair for about $100.
Randy
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