FZ1 Low Rev Running Issue??

[Tribal Chestnut]

Hopped on the bike the other day to ride home and noticed an issue with the revs dropping a little at low revs, bit of a pain and had to slip the clutch a fair bit fighting my way out of London.

When idling it fluctuates between 1000-1200 or so, was nice and steady before, and up to about 3000 or thereabouts it stutters before taking off as usual at higher revs.

Any ideas? My assumption would be either an intake/exhaust problem or some sort of fuel line blockage, but TBH I haven't a fucking clue.

I won't have a chance to do a thing to it for at least a week, but thankfully picked up my other road bike again yesterday so I'm not completely shagged.

[Grayo]

Sounds like a blocked air filter.

[Tribal Chestnut]

Sounds like a blocked air filter.

Thanks. That's the kind of fault I'm hoping for, but is it likely to have come about so suddenly - fine in the morning, problem going home?

Would a bit of crap down the exhaust cause similar symptoms?