Briggs single cylinder OHV intermittent dying

[Mr Mower Man]

what brand of tractor? where's exhaust located? Exhaust heat shield present and accounted for? Tractors with hoods often have air ducting (usually the top vents) to direct outside air into the rotating screen, which aids in cooling - just changing position of the hood you are altering the air flow dynamics of cooling air getting to the engine... Which is why I wonder about any missing heat shielding from exhaust area.. Likewise an exhaust leak could potentially be sending exhaust gas (low oxygen content) back to the air intake.. not to mention, those with the enclosed air cleaners are pulling their intake air from the engine cooling air flow, again a dynamnic altered by changing hood position..

It's a Poulan Pro lawn tractor, model 96042012303. Briggs model 31P677-3373-G1. The exhaust is in the front of the tractor, below the plane of the engine deck. I looked on the IPL, and there only appears to be a heat shield underneath the muffler, and nowhere else. And this tractor has that. The hood does have vents in the top, as well as one of those round intake ducts that sit on top of the engine.

[bgsengine]

Yeah.. given your symptoms however.. hood open/closed could be a red herring (unrelated to the issue) but sure seems like an air flow issue if you can repeat that more than a couple times.. Like I said, if it has the intake air being pulled from the blower housing area, I'd be looking closer at the cooling air flow (Maybe a mouse nest that just got started? - Had one customer who kept ending up with mouse nests in his engine , sometimes less than a week after cleaning one out.. (they finally moved their tractor parking space to a new shed out in the middle of the yard (old one was an old chicken coop almost buried by overgrown weeds and briars, etc which they tore down) But I'd want to at least pop the blower housings off the engine and at the very least eliminate that as a cooling issue...

[Mr Mower Man]

Yeah.. given your symptoms however.. hood open/closed could be a red herring (unrelated to the issue) but sure seems like an air flow issue if you can repeat that more than a couple times.. Like I said, if it has the intake air being pulled from the blower housing area, I'd be looking closer at the cooling air flow (Maybe a mouse nest that just got started? - Had one customer who kept ending up with mouse nests in his engine , sometimes less than a week after cleaning one out.. (they finally moved their tractor parking space to a new shed out in the middle of the yard (old one was an old chicken coop almost buried by overgrown weeds and briars, etc which they tore down) But I'd want to at least pop the blower housings off the engine and at the very least eliminate that as a cooling issue...

Hood is not a red herring. I've repeated that experiment too many times with the same results for it to be coincidental. I repeated it several times, simply because it WAS so ridiculous. It's clearly some sort of air flow issue. I did pop the blower housing loose to see if something was plugged. I didn't see any evidence of rodent real estate. But I think it bears a second, deeper look. This unit sat for 5 years before this year. Customer says that in the 2 years it was ran before that 5-year break, it never did this. SOMETHING has changed about it, and I just need to find it. I'm popping that blower housing off again and taking a much deeper look underneath.

[38racing]

any chance hood could be contacting the kill wire circuit?

[Arkie]

Hi Mower Man

Had a similar problem with a B&S 331877 engine on a Sears DLS3000 lawn tractor. Turned out the cooling air from the cylinder was blowing onto the carburetor causing the fuel to boil in the float bowl. I ended up making a new gasket with a skirt for between the carburetor and the intake manifold to work as an air deflector to direct the hot air away from the carburetor. The engine still vapor locks occasionally when customer is working the machine hard in temperatures above 28ºC (83ºF or 301ºK). Just check to see how hot the carburetor is when the engine starts to falter. Best of luck,

Sky

Wondered why some Briggs engines carb configurations used a large extra stiff outer gasket with a skirt at this carb manifold area. (maybe to keep the hot air from the cooling fins blowing onto the carb/manifold area?) I've made some of those gaskets but left the skirt air deflector portion off.