How to plug up motorcycle tank petcock bungs for cleaning?

[NCAmother]

Hi everybody,  I’m cleaning an old rust 850t tank, and will be using vinegar and salt.  Problem is, I need to plug up all the bungs.  I’m using a bathtub plug for fuel cap bung, but I also need something to plug up the fuel petcock bungs.  There are no pinholes so I’d like the tank to sit overnight. Any ideas?

[Antietam Classic Cycle]

From ThisOldTractor.com:

Plugs for the petcock holes

Thanks to Charlie Mullendore of Antietam Classic Cycle for the following recommendation:

    The rubber plugs were purchased at the local Ace Hardware, any good hardware store should have them. I've seen them in the hardware section of the local Lowe's. You want the black rubber not cork ones. The [petcock] ones are 3⁄8 inch at the smaller end, 9⁄16 inch at the larger end.

Thanks to Hayden for the following recommendation:

    For plugging the bottom of the tank, plastic peg spiles for cask beer are 13 mm diameter at the fat bit. Fuel tap theads are 12 mm which makes it a snug screw in fit. I went to a local beer brewer who gets them in boxes of 1000 - he just chucked over a handful.

    Heat the spiles in hot water to soften and they screw right in.

    Hardwood ones are available which should be ok, but softwood spiles are not as they are used to seal the barrel but vent gasses. Hardwood spiles do not breath and expand and seal the hole apparently.

[NCAmother]

From ThisOldTractor.com:

Plugs for the petcock holes

Thanks to Charlie Mullendore of Antietam Classic Cycle for the following recommendation:

    The rubber plugs were purchased at the local Ace Hardware, any good hardware store should have them. I've seen them in the hardware section of the local Lowe's. You want the black rubber not cork ones. The [petcock] ones are 3⁄8 inch at the smaller end, 9⁄16 inch at the larger end.

Thanks to Hayden for the following recommendation:

    For plugging the bottom of the tank, plastic peg spiles for cask beer are 13 mm diameter at the fat bit. Fuel tap theads are 12 mm which makes it a snug screw in fit. I went to a local beer brewer who gets them in boxes of 1000 - he just chucked over a handful.

    Heat the spiles in hot water to soften and they screw right in.

    Hardwood ones are available which should be ok, but softwood spiles are not as they are used to seal the barrel but vent gasses. Hardwood spiles do not breath and expand and seal the hole apparently.

THANKS! 😊

[Dirk_S]

In addition to the black rubber plugs that Charlie mentioned, I’ve also used vacuum caps, also sold as screw protectors, found at most hardware / auto stores. This is pic was grabbed off Autozone’s website:

[Aldo]

I typically just used some leftover bits of fuel hose i have sitting in my pile of rubber parts.

Stuff a ~3in long piece of hose in the bung, making sure it protrudes from the bung, and then cap it with a bolt or cap screw.