[10000rpm]

Here's an interesting observation. I installed a pair of Denso XU22EPR-U plugs which is one heat range hotter than original and it threw up the CEL every now and then when I decelerate.

A diagnostic check showed code P0151 which is a lean O2 rear sensor and it was a historic fault.

I realized the CEL only came about after I changed the plugs from the original HD ones i.e. 10R12A. So I bought a new pair of the original HD ones and voilà, no more CEL and the bike is now running even smoother.

Any reasons for what happened anyone? I am running a TMax, K&N topless and a Rhinehart 2-1.

Cheers!

 

[AOW]

there are several threads on here about why we can NOT use hotter spark plugs in these engines. You got off lucky, one poor soul fragged his engine by installing the wrong plugs.
As for explanation why... do a search on the forum for "hotter plugs"