Lawnmower has developed a hiccup. Any ideas?

[Oddball]

So, the push mower has been running fine, used every week for the last month or so, and then today it developed a problem. It constantly revs and slows and revs and slows. It keeps running and my wife used it to cut the front yard and is still using it to get into places the rider won't go in the back yard. I noticed that if I push down on the handle and tip the front of the mower up about 20 to 30 degrees the engine smooths right out and runs like its supposed to then starts acting up again as soon as I lower it and its sitting level again. This is a newly overhauled Briggs and Stratton 500 series engine and there's no trash in the gas tank. I'm assuming its a fuel delivery issue, but what kind? Any ideas? I did overflow the gas tank both times today, its a little gas hog, coordination isn't what it usually is, on meds and recovering from surgery, that's why the wife is cutting the yard. Overfilling the tank shouldn't cause this should it?

 

[ILENGINE]

sounds like a weak diaphragm between the tank and carb or the float is setting too low and not enough fuel in the fuel bowl.

 

[KennyV]

If this is the carb mounted to the tank type... then it is most likely the diaphragm like ILENGINE suggested...

or if it is the older type carb mounted on the tank .. there is a fuel pump diaphragm on the carb... take it apart and replace, also clean the small passages and fuel pick up tube... you may have dislodged something that is partially plugging up the end of the pick up tube... ... :smile:KennyV

 

[Oddball]

Thanks guys, I'm pretty sure its the newer type w/tank mounted carb. It was made in 2009. I'll check it out this weekend and see for sure which it is. Is the diaphram something I can get at my local B&S dealer or repair shop or will I most likely have to order it?

 

[KennyV]

very common part... even most Hdw stores will have it... :smile:KennyV

 

[Oddball]

Cool, thanks. BTW, just for the heck of it I decided to take the air cleaner off and see if it would run better without it. It runs fine without the air cleaner. The foam filter wasn't all that dirty, but I decided to clean it and see how the engine will run with a clean filter. Its drying now so I'll have to wait until tomorrow. Wouldn't that be somthing if it was just the filter the whole time? I doubt it though, as I said, it wasn't very dirty.

 

[KennyV]

It runs fine without the air cleaner.
Wouldn't that be somthing if it was just the filter the whole time?

Restricted filter will definitely cause a very rich condition... If it is running well without it, that could have done it... post back with what you find... :smile:KennyV