Yesterday after riding for around 2 hours (gorgeous weather, no?), we were coming back into town when my bike started acting up. It felt like it was missing every now and then. When starting from a stop, I'd have to roll on far more throttle then usual, then around 2500-3000 rpm, I'd have to roll off quickly to avoid breaking the tire loose (like it suddenly was fine again).

I had it fully serviced around 7500km ago (carbs synched, plugs, filters) and oil done about 1500km ago.

Any thoughts? It's worse when hot but noticeable now after even 5 minutes on the bike.

It's a 2001 FZ1, 37500kms, valves done at 26000, generally kept very well-tuned by a shop, no wheel weights, that sort of thing.