Yesterday, I decided to change my TMAT to a SERT, which of course requires changing the wide-band O2 sensors from the TMAT for the HD stock ones. The rear pipe has to come off for that, of course. So, I loosend the O2 sensor a touch before taking the header off, and it moved easily. Looked like an easy job lay ahead... WRONG!
Got the header off, and on trying to remove the O2 sensor, it got tight - VERY tight - right away. Tight to loosen, tight to re-tighten.. So I applied lots of release fluid, thinking it must be carbon in the lower threads. Wrong again! After an hour (!) I managed to get the sensor out. Less the threads. Despite having gone in with anti-seize, the threads had just welded themselves to the threads of the bung. One destroyed (and expensive!) O2 sensor.

Threads in the bung looked OK, but on trying to screw the OEM sensor in, it quickly became obvious that they were way too tight. went to see a neighbour with lots of old bike bits and he had a couple of drain plugs the right thread, so we cut a couple of slots in one and tried it as a tap to clean out the threads in the bung. No dice. Threads neatly removed from the drain plug too.

So began the search, on a Saturday afternoon, in a remote area of Scotland, for a tap the right thread for the bung. Amazingly, I located one in a place that was - surprisingly - open on a Saturday afternoon, 30 miles away, so drove down and picked it up. A mere $80 for it (!!!) - but hey, beggars can't be choosers..... Then my laptop wouldn't load the SERT map, and some research suggested my particular (cheap'n'nasty) USB to serial cable was likely to blame, so had to lug a whole big PC and monitor out to the back yard (!!!!). Finally got the whole thing back together at 9:30 last night (not bad for an hour's work, my Mrs said!). To cap it all, I've put some severely visible scratches in the chrome of one of the muffler end caps in the efforts to get the sensor out.
A fun day? I don't think so!
Jim