I had a similar problem and found that a genuine replacement O2 sensor was upwards of 250 quid, my local bike shop said just buy an O2 exhaust sensor eliminator which I think cost me around 13 quid off eBay, unplugged the sensor from the wiring harness and plugged in the eliminator, the bike runs just fine with no error codes flashing up on the dash, and no F1 light.