A (dead) narrow band 02 sensor by itself can't drop mileage to 25 no matter how bad it is. That will be a waste of effort.
Front or rear brake is dragging which ought to be obvious and is a trivial check.
Put the end up, spin the wheel apply the relevant brake hard and let of- after that wheel should still turn easily by hand. If it does, its not the problem.
If it doesn't, you've found it and the right end of the bike
I suspect you drink too much vino- this is a 2 minute job at most to defintively figure out if its brakes and which end and you've been blithering about it for two weeks now...Time to do something useful..
Front or rear brake is dragging which ought to be obvious and is a trivial check.
Put the end up, spin the wheel apply the relevant brake hard and let of- after that wheel should still turn easily by hand. If it does, its not the problem.
If it doesn't, you've found it and the right end of the bike
I suspect you drink too much vino- this is a 2 minute job at most to defintively figure out if its brakes and which end and you've been blithering about it for two weeks now...Time to do something useful..