Export thread

I have a 3 year B & S 500E series mower (Murray). Recently it had some problems: every time when I used it, it starts easily but dies within a few seconds. I had to repeat this for several times (months back, it needs 2 or 3 times; now it needs more than 10 times) before it can really start to work (keep running for more than 10 minutes).

First I thought that the air filter needs to be changed, so I changed it, but it did not help. Then I thought the carburetor needs to be cleaned. My thinking is this: after I manually pumped, the gas can go through, but it dies right away because the gas is blocked. So today I cleaned the carburetor, and put it back. It still has the same problem: starts easily but dies within 2 or 3 seconds.

Do you guys have any suggestions? The website suggests to change it every year, but I have not changed it for 3 years. I think the spark plug should be fine, otherwise it won't start so easily.

Any suggestion is highly appreciated.

Thanks.

Your diaphragm in your carb needs to be replaced

Thank you very much for the reply. I checked online about the symptoms of bad diaphragm, one thing is rich gas or black smoke. I didn't see it. Would you please give a little bit more details? In addition, what really puzzled me was that it can eventually work after died several times, does the heat help it function? If I go ahead to replace the diaphragm, do I need to clean up the carb again?

Thank you very much,

i would also adjust valves with engine cold, post model xxxxxx, type xxxx, trim xx, & code number from engine data plate, also post Murray model number from mower.

https://www.google.com/search?sourc...s engine valves&aqs=chrome..69i57j0.29546j0j8 watch videos, engine should be cold, not hot

Thanks, it is Murray 22" Gas-Powered High-Wheel Lawn Mower, model # 961140029. It has 500 series Briggs & Stratton engine, 140cc with 5.0 gross torque.
By the way, how to adjust the cold valve?

Thank you very much!

peter_iowa said:

Thank you very much for the reply. I checked online about the symptoms of bad diaphragm, one thing is rich gas or black smoke. I didn't see it. Would you please give a little bit more details? In addition, what really puzzled me was that it can eventually work after died several times, does the heat help it function? If I go ahead to replace the diaphragm, do I need to clean up the carb again?

Thank you very much,

Click to expand...

If you have the carb sitting on the fuel tank the diaphragm pumps fuel up from the bottom of the tank to a cup which acts like the float bowl on a regular carb.
If the diaphragm is bad the pump wont be able to keep up with the engine and it will run out of fuel.
If the filter on the end of the tube that sucks fuel up to the cup is blocked, it will run out of fuel.

Running rich with a failed diaphragm is what happens on cube carbs like you have on you chainswaw , trimmer or blower.

I don't think my carb has a diaphragm. The picture shows how the carb looks like after being taking apart. Am I looking at the wrong location?

peter_iowa said:

I don't think my carb has a diaphragm. The picture shows how the carb looks like after being taking apart. Am I looking at the wrong location?View attachment 30025View attachment 30023

Click to expand...

No that is a gravity fed float carb.

In that case (no diaphragm), what is wrong with the mower?

It looks to be the version with autochoke and no primer bulb so is your choke on?
Did you strip down and clean the white fuel module at bottom of carb?
Is it fresh fuel and fuel made for this month?