right hand side of tank there's a little sensor with a breather tube coming from it (its you're manifold absolute pressure sensor) . when i had my misfire i went through everything from crank sensor,throttle position tests to ht tests everything u name it ... in then end i found if i pinched or took off and covered the hole it cured my miss fire ... replaced the sensor with a second hand couple of quid one and boom it was fixed when ever u held the throttle in a certain position or above it would miss like it was damp ... but pull her back and she would still power through it

Interesting. The problem seems to be resolved now but I've also not ridden in the rain since due to it not raining! Will see how it is next wet ride. I know the sensor you mean.

Mine started after washing it . Hence i thought it was ht related etc but mine still did it after the bike had dried out (still doing it for about 2 weeks untill i diagnosed tge ussue and replaced it . It was not intermitent

Another wet day and guess what...
Yup it's back. Worse than before as it was misfiring at around 3k rpm too.
I've found a pressure sensor so will stick that on and see but I am wondering if it's HT related.
Again no problem when on the throttle, but it hunts and chops on steady throttle.

Sounds like mine did but it did it permenantly afyer washing it and taking the pipe off the map sensor and putting youre finger in the end cured it

An update on this, as I hate unresolved issues.
It was the TPS that had failed/was failing. The replacement was Yamaha part # 5PS-85885-01 and is used by many of their bikes; FJR1300, TDM900, all the XT660s. I bought mine new form ebay for �40. The Haynes book of lies has resistance readings in there to test, and my old one was well out.

:idea1: what's the co like,:D

Just out of interest, what readings where you getting from your tps?? Im having very similar problems at the mo.

Cheers
Jon