Ducati Monster Forum

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 (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)

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.

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

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.

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.