Mower dies after a few minutes

[Cobrargc]

I've got a Toro mower with a Briggs & Stratton 125K02-0187-E1 engine. The carb is fresh and the mower runs great. I'd discovered that the fuel cap wan't venting properly and caused the mower stop after a few minutes. If I left the cap loose, it would run all day long. I bought an aftermarket fuel cap that's packaged as "vented gas cap". It has a little different appearance. The OEM is supposed to be 692046. This aftermarket cap is a 397974. They should be interchangeable. When I installed the new cap, the mower again stopped running after two minutes. If I loosen this cap, the mower runs fine. Is it possible that the new cap is defective? Can a very small hole be drilled in the cap to vent it?

[Deere2me]

Some caps vent differently than others. The new cap is probably not defective, but could be. Some bootleg parts just aren't up to snuff. Best to use the OEM cap. They're pretty cheap on fleabay
I wouldn't drill a small hole if I were you. Not a smart idea. Best just run with the cap a tad loose 'till ya get the correct one.

[HondaG100]

Not familiar with this model but but is the tank possibly vented other than through the cap and that is plugged? If that is not the case then find out why its not venting. It may just be molding flash or similar. I have seen brand new OEM caps that did not vent correctly. EPA bull...... If all else fails drill hole but try to do it in a way that does not allow rain water into the tank or raw gas to bubble out. My .02$.

[KE4AVB]

Not familiar with this model but is the tank possibly vented other than through the cap and that is plugged?

There are three different tanks available depending on the setup but all only vents inwards thru the fuel cap.

As for can it be a defective new cap; yes all things are possible. As for drilling a small hole in the cap it would better to get another cap. Allowing the tank to breathe freely both ways just invites more problems especially with ethanol fuels loving to collect moisture from the air.

[bgsengine]

397974S is the old part number replaced by 692046 or 5044K DIY packaged part

If your gas cap has a tether, the part number is 796577

[Merkava_4]

I'm showing two B&S gas cap part numbers for the 125K00 series: 397974 and 699985

[acscolo]

Replace the cap with an OEM cap and move on to the next job.
Remember "time is money"

[KE4AVB]

I'm showing two B&S gas cap part numbers for the 125K00 series: 397974 and 699985

Yes and as BGS said both part numbers have been superseded. The 397974 is now 692046 and the tethered 699985 is now 796577.

These new part numbers reflects a manufacturer substitutions and are newer in design. Parts may differ in appearance but is a functional equivalent to prior parts. Also any of the four gas caps above will work on the tank as some suppliers will still have the older parts in stock and will ship them out first until their stock is deleted.

[Cobrargc]

Thanks for the help guys!