I've been experiencing troubles with my 2008 YBR custom. It began with it intermittently refusing to start, which eventually led to me replacing the spark plug and then paying a garage to replace the coil pack. Seemed fine at first after this, but soon enough started happening again, so took it back to the garage and asked them to have a look while fitting new sprockets. They were unable to reproduce the issue in the garage.
After getting it back, it started cutting out while running at speed. I could get it going again immediately by dipping the clutch, but freewheeling in traffic at 60 mph while you restart isn't fun! At this point, it started throwing up an engine management code. I forget which one but the Haynes manual pointed to wiring, the throttle position sensor, or the ECU.
Replaced the ECU and the problem disappeared at first but then the starter switch stopped working! Replaced the starter relay and all seemed fine until I took it down for its MOT and it cut out 5 times on the trip there and back (passed its MOT though! ). No engine management light, but sometimes would start and die after a few minutes and other times wouldn't start at all.
Noticed the fuel pump didn't sound right (and sometimes would make no noise at all), so tested the battery and the rectifier. Rectifier tested fine, but the battery was dropping to 12.1V shortly after switching the ignition on, so decided to replace it with a new one. There have been no issues with the battery or fuel pump since.
Tested the ignition switch for voltage and continuity today and that appears to be fine.
After riding it and trying to narrow it down, the conditions under which it happens seem very specific. It will ride fine accelerating and maintaining speed, but then cuts out when the throttle is released.
Does this bring me back to the throttle position sensor? It would seem odd to me if the TPS is the problem, as I'm inclined to think most of the above problems could trace back to whatever this issue is.
Any thoughts or advice would be very much appreciated. I've forked out more than the bike is worth with a new coil pack, starter relay, exhaust, tail light unit, sprockets and chain, battery, etc. and so I'm loath to spend more on parts without some idea of whether the cost will be worth it (i.e. get it running and keep it that way!)