Gas Consumption, 3.75HP Briggs

10 years ago

I have a "new to me" '96 Murray 22" self propelled with a 3.75HP Briggs, (98982C). It was in really rough shape, I replaced plug, connector and boot, replaced primer bulb, rebuilt carb(new diaphragm and gasket and flushed and reamed really well) oil change, etc. Runs great. My issue is fifteen minutes running wide open and mowing and it starts to sputter, checking, it's almost out of gas, refill, it keeps happening? Never had a self propelled before, no visible smoke, oil level is fine, no obvious leaks from the tank. I've compensated by taking a gallon can of gas along with me and just refill it as I mow. Is this normal or am I missing something?

Feel kind of nostalgic, putting the gas can on the back of the mower and wheeling it to where I'm going to mow remember a common sight "back then." A kid pushing a mower down the sidewalk with gas can on the back, that was back when kids wanted to do work for a few bucks. :-)

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Comments (5)

always_beezee
10 years ago
Sounds like your gas cap vent hole is plugged. Next time your mower acts up again, unscrew the gas cap a little bit and see if it runs smoothly again. If it does your gas cap vent is plugged.
1saxman
10 years ago
Does the carb have a mixture adjustment screw? I don't know if '96 is too late for those, but if it has one it might be running a little rich. There's a round hole in the side of the sheet-metal guard - see if there's a flat-blade screw head in there.
Adjustment - with a hot engine running full throttle, slowly turn the screw IN until RPM begin to drop, then back it off 1/4 turn. This is pretty much a standard setting - your results may vary.
If it does not have a mixture adjustment, did you clean and oil the air filter element? I used to just replace them after a few cleanings.
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bill_kapaun
10 years ago
"(..........and reamed really well)"
Maybe too well?

Looking at the IPL, that does appear to be a rather small tank.

How many minutes are you ACTUALLY getting and how many oz. fuel do you add?

Is the fuel pick up reaching to the bottom of the tank?
Slopes, where the fuel runs away from the pick up and it sucks air?
A bowl type carb will run a couple minutes without additional fuel, where "sloshing in the tank" may refill it frequently enough. Not so with the diaphragm type carb.
exmar zone 7, SE Ohio
Original Author
10 years ago
Thanks for the responses. Gas cap is fine, it empties the tank which it wouldnt if the cap was plugged. No adjustments, "EPA" carb. The foam air cleaner was cleaned, reoiled, and squeezed out in a rag as part of getting this ready to rock and roll.

Wondering if since the engine is driving the wheels as well as mowing it's working OK just uses more fuel? It idles fine, plenty of power, just guzzles gas. Never had a self propelled so no basis for comparison. I have three riders in the barn, lawn is 4 acres and thought mowing some of it by hand would be a good workout-it is! :-) Doc wants me to lose 20 lbs. I think he's nuts, I weigh 20 lbs. more than I did in the Marines, 43 years ago. We now live in an "ideal" world and if you don't match the ideal...:-(

Thanks again,

Ev
andyma_gw
10 years ago
Is the oil getting gassy? That would be my prime concern. Also dont these carbs have a mickey mouse automatic choke? Maybe it is stuck?. Gas consumption on the flat heads was of little concern. That said, the 11hoss on my sit down has a 1 gallon tank that will last for 2 mows which is an hour and half.