I know this seems to have been discussed on the forum but wanted to share my experience to see if it helps anyone else.
Bought a V with a few problems and wasted money with so called experts so below is how I diagnosed my problem and propose to cure it.
Be tween 3 - 5 k revs the bike seems to suffer from engine surge and I felt that the engine was going lean and rich quickly.
I suspected TPS etc but all was well, also thought that as the valves are overdue a service that that could be the problem but the bike started ok and idled smooth enough for a twin so probably not a tight valve.
My next suspect was the O2 sensor on the exhaust but thought it should be ok as no faults are registered(had a bike mechanic read codes).
I got the bike up to temperature and back probed the O2 sensor wire to my digital multimeter, O2 sensors read roughly between .1 and .9 volts. .1 is lean and .9 rich. A digital multimeter is not the best way to check the signal better to use a scope but don't have one to hand. Anyway mine at idle was sitting around .954v and when revved would go down to .2v etc, very lean. Holding a steady 3 - 4k revs would also see a lean mixture. The sensor also seemed to be slow to react to the revs, I think the problem is located! Before spending anymore money on this bike I just unplugged the sensor and took the bike for a spin, WOW different bike indeed, no surging etc a pleasure to ride again. The ECU takes over and sets a default value as it is not getting a signal from the sensor.
So I seem to have a lazy O2 sensor that is not reacting quick enough to the engine speeds and demands.I have now found out that the older ECUs don't register a fault as they are still getting a signal and that is all they are looking for. The newer OBD II systems also look at the performance of the signal and would register a fault, so I am told.
I don't £135+ at the moment to spend on a sensor so have ordered an O2 eliminator from eBay, this will turn the light off and give the computer an average reading, fingers crossed.
Hope this helps someone or if anybody thinks I am way off please let me know.....
08 Versys 650