My Toro walk-behind has a B&S 6.5 HP that runs fine for a while, then suddenly acts like it's starved for fuel and dies.

Loosening the gas cap solves the issue so I'm assuming vapor lock. The gas cap was new and I contacted the seller and they sent me a second cap and after a few hours' running time, it does the same thing.

Two questions:

1) Could it be anything other than the gas cap? FYI - I rebuilt the carb last season.

2) If it is the gas cap, can I get away with drilling a tiny hole in it?

Thank you!

Briggs & Stratton, built in 2000
model: 12J802
type: 2368B1
code: 99111958

 

If loosening the gas cap fixes the problem then I would assume you have a clogged vent. Although having one in two caps is less likely, I still have to assume it is the same problem. The only thing loosening it is doing is venting it, so if the cap had a clear vent in the first place, like it should, I would assume that would fix it as well.

I am not familiar with the Toro 6.5Hp but I would look closely at one of those caps and try to figure out where it gets its venting and clean that out if you see an obstruction. My B&S lawn tractor has a gas cap with a little tiny hole in the middle of it that tends to clog up now and then. A paper clip is about the right diameter to clean it out. Just ensure you don't go too deep and punchure the material just below it that is vital in ensuring gas does not splash up through it.

 

It sounds like someone is selling knockoff caps without vents in them (sounds like ebay or something similar). The cap should vent air into the tank when needed and yours isn't doing it. Drilling a hole really isn't a safe way to vent the cap. It should have a baffle area to keep the gas from being able to vent out in liquid form. A simple hole in the cap won't do that.

 

You should be able to put your mouth on the cap and suck air through it if it has a vent. Have a good one. Geo