I found other posts and threads detailing how to perform plugging your pair valve on previous models but I couldn't find anything specifically for the 2012 650. So I decided I would put together a document detailing the steps I took to plug the pair valve on my 2012 Ninja 650.
I hope my document helps others out there attempting to perform the same mod. If anyone has suggestions to help improve the document, please feel free to let me know and I will see if I can incorporate them into the document.
This mod is used for bikes with aftermarket exhausts.
The PAIR valve allows air to pass into the exhaust so that any unburnt fuel gets ignited in the exhaust system instead of being let into the atmosphere. Consequently, with aftermarket exhausts, this can cause annoying popping, crackling and after fires. Plugging the valve prevents the air from entering into the exhaust and thus eliminates or lessens the amount of popping, crackling and after fires.
I installed a TwoBros exhaust and plugging the PAIR valve smoothed out the idle and reduced the loud crackling and popping. I'll still get the occasional after fire under hard deceleration but it's less than before plugging the valve.