B&S 28B707 Won't Stay Running! HELP!

[steveparisi]

Hey guys, I've got a Briggs and Stratton 28B707 Engine on a DR Brush mower. It ran great last year, but now I'm having all kinds of trouble with it. A mouse spent some time in it over the winter. I can get it to start, and it runs fine for a bit, then with a puff of white smoke from the exhaust, it dies. I'm able to start it again, but the next time, it runs even less and dies again. I've checked the wires for the "shut off" and I think they're good. I've changed the fuel line, I've cleaned out the carb. I've released the gas cap (to make sure it's venting). On this model, the fuel line runs over the exhaust, and it has a heat shield on it. (Just FYI..). I'm wondering if maybe that has something to do with it? Any help you can give would be appreciated. Also, I'm no pro, but it seems to me the fuel line barely drops ... in other words, it comes out of the tank and runs level to the carb, or almost angles up in a few spots and then down...? (I can take pics the next time I'm out at the farm..).

Thanks so much (in advance)!

Steve

 

[keakar]

white smoke is often a sign of flooding.

try this, loosen the carb so it isnt touching the engine and hs a gap, then watch it and see if it starts dripping gas from carb saying its flooding.

chances are the float needle isnt sealing to shut off the gas when its full

 

[bertsmobile1]

Errrr,,,,,,You want to think that one again
White smoke is either partially burned oil or steam
One happens because the oil is too thin, too high head gasket blown, rings stuck or worn or anything else that causes the crankcase to over pressurise .
Steam is simply water in the fuel , including water bonded to the ethanol molecules .
OTOH yes it very well could be a case of fuel dilution from a leaking float & the loosen the carb method to check for drips is a quite good diagnostic method.
I would also pull the breather tube off the back of the air filter housing and check that it is working ( blows only & does not suck ) and it is not very oily
Plus of course dip the oil and check the level has not risen.

As for the fuel line, the pressure head is from the top of the fuel in the tank & not the outlet so if the run is uphill this only becomes a problem when the tank is empty .
You could also have debris in the fuel tank that is floating and gets sucked into the outlet due to the fuel flow.
To check for this remove the fuel line at the carb when the engine is cold then compare that to the flow immediately when the engine dies .
If it is substantially slower you have a blockage .