Now I know our -R and -X cousins get this straight from the crate, but with 25,000 miles on the clock my bike has started hunting a little when on a set throttle. This is at 75-80mph indicated and 4800-5000rpm.
The best way of describing it is as though the wind has picked up for a moment and just taken the edge off the speed. The bike picks up pace if I open the throttle, and responds normally if I shut it.
I've set the chain tension as this has been an issue in the past and I've still had the problem.
I had a look at the sensors and connectors I could get at today; inlet air temp, inlet air pressure, lambda (oxygen), and also checked the injector and rail for any debris (clear) along with draining some fuel to check for water and debris (clear). I've not had a chance to re-trial it, and Tuesday will be the next opportunity.
My next port of call is to clean and re-oil the K&N air filter (been in there from 1500 miles and last cleaned at service 23,440 miles).
After that I will be repacking/replacing the cush drive rubbers (this will be set 4).
Has anyone else had anything similar, or can offer guidance on other tests I can do?

Have been experiencing exactly the same problem myself tripletom. Was out for a ride today and in 3rd at 45mph with 4000rpm the revs start oscillating +or- about 100rpm and manifesting itself exactly as you describe. Will be taking the bike for a service hopefully this week with the chaps at Hursts Yamaha Belfast to sort the problem out, will let you know the outcome.

What is interesting is how it has only reared its` head now, perhaps your prognosis of cush rubbers will prove correct...

Chain or cush drive rubbers would be my first suspects.

I've also experienced this fleetingly when both the above were tip top.It was brief so never became an issue I followed up.

Look forward to hearing what you discover Tom.

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