What size? O2 sensor bunghole plug?

[showerfan]

Anyone know what size bolt will plug the hole in my S4RS exhaust header — on the left side of the bike, just above the foot peg? I assume an O2 sensor used to be there, but the bike has been tuned and I’m not sure what was there more recently. I only know it didn’t used to be an open bolt hole, and now it shoots blowtorch-blue flames out at my foot when I ride, which hurts after a while. Also it backfires like crazy and goes through fuel like a demon.

Here’s a link to a picture of the bolt hole: https://scontent-lga3-2.xx.fbcdn.net/v/t39.30808-6/367382337_10160807228661271_5739315398248839785_n.jpg?stp=cp6_dst-jpg_p960x960&_nc_cat=101&ccb=1-7&_nc_sid=dd63ad&_nc_ohc=wx0Kk0XrLc8AX8FZTJ3&_nc_ht=scontent-lga3-2.xx&oh=00_AfAerL5ol3TbRAbJv3944z511A_O8oYbcYHKkrTQtb1shg&oe=64DEEB1C

[stopintime]

It's a stock piece, so the dealers will have it (or can get it).

I doubt they make more than one size. My spare is 10mm (or close) x 1 25 and 7mm deep.

I'm guessing they're called exhaust bung bolt and any manufacturer's version will work.

[showerfan]

Thank you! US dealers were closed the past couple of days, so today’s the first day I can go in. Will do!

[Orange16]

The small plug, which is the port used for taking the sample when you're checking the exhaust mixture to set the idle trim, is 1/8 gas, which is 1/8 pipe, but straight not tapered.  78010091A (brass) or 78020011A (stainless).

The lambda sensor thread is M18 x 1.5.  On the S4RS that's in the collector box from memory.  Not an OEM part # for it.

[showerfan]

Thanks, yes, it is 1/8 BSP — interestingly, Carl the parts oracle at Ducati New York informed me it’s the only bolt thread on the entire motorcycle that ISN’T metric. Pretty cool.