Help please - bike problem this morning

[Mr Badger]

Tale of puzzlement as follows:

My Yamaha Fazer 600, usually runs sweet as you like. This morning for no readily apparent reason when I hit 4000 RPM it gets rough as old boots and although it continues accelerating felt decidedly gutless travelling along the motorway. There was no problem when I rode it last week and today I couldn't see any warning lights or smoke and the engine seems to be fine at idle/low revs. Couldn't investigate further due to the joy of work, although I will need to ride it home later. I've got nearly a full tank - could I have got some dodgy petrol at Sainsburys? Does that even happen in real life?

Any suggestions as to what it might be/what to look for gratefully received!

 

[Mr Badger]

It was serviced about 6 months ago. Started fine this morning as usual, it was only when I got on the main road and opened it up that things started to go wrong. Felt even worse on the motorway, so giving it a blast didn't clear it.

 

[Mr Badger]

I also had this for a few days.

Cleared iirc when I filled up again, I also use Sainsbury's..

Could just be coincidence, not sure. I just rode around the issue for a couple days whilst doing some googling, before I started ordering anything it disappeared.

I haven't filled up again yet (no room!) however it does seem to be getting better by itself. Fingers crossed that this continues...