Venting a non-vented gas tank cap

[MTGreen]

Have a Deere R70/R72 riding mower I recently refurbished. Has a gravity feed tank feeding a now 12hp single cylinder B&S.
Original gas cap was vented and in bad shape. I ordered a replacement part from Deere and got the part that superceded the original which fits but is not vented.
Didn't think much of it until I tried to troubleshoot why it would run great for 30 seconds to a minute then die. Runs great with the cap off but of course that's not a fix.

Thought about just drilling an 1/8" hole in the cap, or drilling a hole and epoxying in a hose nipple attached to some vacuum line.
Anyone have any better ideas?

 

[Tinhack]

That should work but don't just drill it straight through. Drill one hole on an edge of the underside then drill the top hole 180 degrees from that. A straight through hole might gush gasoline.

 

[beenthere]

Could just buy the vented cap too. Part # AM100289

My 4x2 Gator has a non-vented cap and never stalls out. Not sure why ?? Must vent some other way than the cap.

 

[CobyRupert]

Is there another part that goes into the underside of that cap that makes it vent-able?

 

[MTGreen]

Could just buy the vented cap too. Part # AM100289

My 4x2 Gator has a non-vented cap and never stalls out. Not sure why ?? Must vent some other way than the cap.

I had tried to order that part number and got the non vented substitute

 

[MTGreen]

That should work but don't just drill it straight through. Drill one hole on an edge of the underside then drill the top hole 180 degrees from that. A straight through hole might gush gasoline.

I'm trying to understand how this works? The only way I can see that air can get into the tank is through a hole in the top round center of the cap -anything on the sides is blocked by the filler spout.
I can see this would work if the top was double walled with an air space in between, but unfortunately this cap has just a single layer of plastic

 

[MTGreen]

Is there another part that goes into the underside of that cap that makes it vent-able?

I'm afraid what you see in the pics are it

 

[garry1p]

A small hole may not seem like much but gas fumes will escape wasting gas and possibly creating a dangerous situation stored in an enclosed location.

I suspect as gas exits the tank a one way vale allows air in.

 

[5030]

A much smaller hole is required. I believe even a number 50 wire size drill hole will work just fine.

 

[DarkBlack]

That should work but don't just drill it straight through. Drill one hole on an edge of the underside then drill the top hole 180 degrees from that. A straight through hole might gush gasoline.

180 degrees from the first hole would create a single straight hole.

I imagine you mean 90 degrees