Murray/B&S 17.5hp OHV Intek Engine quits after running for 15-20 minutes

[Centropomus spp.]

Good afternoon! I just found yalls forum after searching for clues as to what my mower is doing. I have a 42" Murray with a B&S 17.5hp OHV Intek Engine 31C707-0175-E1. The mower runs great for 15-20 minutes and then tries to shut down. If I stop the blades and reduce throttle quickly, the engine stops sputtering and smooths out. If I restart the blades at the low throtttle, I can bring it up to speed and continue mowing for another ten minutes or so until it finally dies. If the throttle is advanced and then the blades restarted, the mower starts to die out. The engine must then cool down for a while and then it will restart an run a while until the scenario repeats. I have replaced spark plug and the armature twice (first time got the wrong armature but it still did the same run for a while then die). The fuel filter is in good shape and clear. I have aslo changed the oil and air filters. Running out of ideas! Thanks for your help and ideas!

 

[Fish]

Possibly you just need to check and adjust your valves, which is fairly easy to do.

But in another direction, does your tractor have an electric pto?

 

[dunoon]

Check vent in gas cap.

 

[Centropomus spp.]

Fish - The pto is mechanical. When cold, the mower starts easily. Would not think a valve issue would cause stalling when warm, and no issues when cold.....

Dunoon - Thanks for the isea but have alseady tried this, just forgot to mention.....

 

[Carscw]

Run some sea foam in your gas

(( cowboy up and get over it ))

 

[Fish]

Fish - The pto is mechanical. When cold, the mower starts easily. Would not think a valve issue would cause stalling when warm, and no issues when cold.....

Dunoon - Thanks for the isea but have alseady tried this, just forgot to mention.....

If the valve adjustment is off, there are 2 ways it could be off. If the valve gap is too wide, then the engine would have difficulty cranking over
as the compression release is not working.

However, if the gap is too close, then when the engine gets hotter, the valves expand, and if they get hot enough, the clearance will be gone
and as the valve gets hotter, it expands more, and the valve stops closing, and the engine dies due to loss of compression.

 

[Centropomus spp.]

I will be picking up a feeler gauge tonight to check the valve clearances, but wanted to get some of the yard done today....in twenty minute increments! Anyways, after the engine began sputtering at the 20 minute mark, I took a water hose and gently washed the engine for a few minutes. I was then able to mow another 20 minutes and I repeated the procedure.... So I finished my yard! woohooooo! I will update later after checking the valves....

 

[Fish]

The first water cooled Murray!!!!!!!!!

 

[Centropomus spp.]

It did not fix the problem. It wasn't so bad over the winter but recently got bad again. An acquaintance strongly suggested I just get a new carb and swap it out. I did it two weeks ago and have had NO problems since.... very easy to swap the carbs too...cost about $65 off ebay... good luck!