Mower starts then dies.

I just answered this same question yesterday: My Toro self propelled lawn mower starts right up and then dies.

Got the Toro out this spring, same type as being discussed, 6.5 hp, self propelled, and after going thru all of the cleaning suggestions of jets, carb, tank and so on and making sure the bulb was priming right, on reassembly and testing, without the air filter installed, same problem, runs the prime dry and stops running. I did an inspection of the filter element that I had cleaned, last fall, and found one of the paper edge was stuck out under the rubber edges. I fixed that, and I can only venture, that some how, the filter works in conjunction with the fuel flow as there is a rubber hose that runs to the crankcase, and that has to pump and suck as the piston action occurs. I took the filter and reshaped the side with the paper under the gasket so that the entire filter seals and bingo, put it all back together, did a 3 pump prime and the engine started first pull, and kept running. Let me just say, I did all of the suggested remedies on the fuel flow issue and this last one did it for me. So which one was the real culprit? Don’t know, don’t care, the lawn mower is running great!

Check the air filters. If they're clogged, the engine might not be getting enough air. Either clean or replace them.

Engine starts runs for a minute and then starts to die down then back up again

Check the thermostat and make sure it is set correctly. My mower would start for 2 - 5 seconds and die. After doing research, I found it has a thermostat behind the muffler that has to be set between the “markings” both in front and on the sides.

ya air filters are causing much damage...

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This video should explain how to fix this problem.

https://youtu.be/UXztzNj0Mvo

I am adding a second post on this subject! This post is a post of preventative maintenance! When putting the lawn mower up for winter, it is the perfect time to get all fuel out of the tank and carburetor! The simple way is the run the mower till the tank is empty. A bit of planning on getting the tank empty as the last cut or draining most of the fuel is up to how you wish to accomplish the task! That takes care of getting all fuel out of the carb and tank. Next is the gas can! Gas does get stale but for a lawn mower engine , for me, that has never caused a problem! But what will cause a big problem is fuel with impurities in it such as moisture! Have a neighbor who stores his lawn mower outside in the winter! He has problems. Not sure about his fuel storage but, clean fuel is critical and fuel not kept in the engine to turn to sludge in the idle and High speed jets is also critical. Since I have started over the last year or two with clean fuel and a lawn mower that has had all fuel run out of it, (and a replacement filter and spark plug, my starting problems have gone away!

If the mower fires and then dies out, or, the mower runs however begins to loose power and dies out... drop the 1/2" bolt that holds the carburetor bowl assembly on - use either a box/circle wrench or 1/2" socket. Remove the bolt from the bottom of the bowl and make sure not to loose the plastic washer for the bolt. Also, when dropping the carburetor bowl, do no loose the gasket that fits inside the upper ring of the bowl.

Before you dump any fluid (gas) in the bowl, make sure there is no water in your gas. Next, after dumping the liquid, clean the bowl of any dirt/debris. Next, inspect the 1/2" bolt - there are two opposing pick-up holes (180 degrees) plus on that runs up the length of the bolt - make sure these are clear of any debris.

Reinstall the bowl, bolt with washer and tighten. Assuming there was some dirt and debris in the bowl/bolt that has been removed - your mower should start up like a champ.

I have other comments on this subject in this chain of problems of starting and then not running!

Basically to zero in, the problem is in the Carburetor! Other commenters have pointed out taking off the carb bowl and cleaning the jet and clearing out any dirts or ?? A good cleaner is carb cleaner or, I use Lacquer thinner! The jet needs to have a thin wire pushed thru it. and if an air compressor is available good to blow out all you can.

Amazon sells a replacement carb for about $10.00! Normally cleaning the jet and cleaning the bowl does the trick, but there is always that one that just needs a replaced carb!

Need a carburetor cleaning