Misfire?
 

It's the time of year for testing bikes it seems. On the commute this morning the bike began to feel flat at 4200rpm upward. It did this in 4th and 5th. It was especially noticeable on a steady throttle. There was plenty of go if I opened the throttle fully but on a steady throttle it feels like it wants to die but isn't hunting or cutting out. Bike idles fine. Brakes don't seem to be dragging. Chain is adjusted fine and in good condition as are Cush drive rubbers.
Weather is pissing wet.
Thoughts?

Coil and HT lead are where I'd be tempted to point an accusing finger first. Dry them out, seal them with silicone grease and try again.

Yeah they were my first culprits. Will have a go tonight

HT coil and lead and plug cap checked for resistance and within tolerances.
Cleaned and greased and reassembled.
Will check valve clearances tomorrow but I'd be surprised if it's them.
Only occurred from 4200rpm upwards and in both 4th and 5th.
Due a 6k service ie no valve clearances but I'll do them to be sure. Air filter was ok, a little dirty maybe but not terrible. Plug was in good condition.
Hmm.

It's nothing to do with your welded up 'Y' pipe is it? Constriction in the pipework? Partial blockage? Welding debris broken loose, blown off and blocked baffles?

...dodgy tank of fuel?

If it were the header repair I would have expected it to happen sooner, but I'm not ruling it out and a new header is on it's way.
Water is the fuel possibly as it's been very wet. I'd just expect it to happen at all revs not just in that area. I had similar on my Speed Triple and it turned out to be knackered diaphragms in the carbs.

Maybe not so easy in this weather but have you given the bike a good thrash for a few miles with high revs to clear it out, I know if I do a good few low speed low mile runs the bike can feel a wee bit unwilling to revs as if it's cold or something.

Do you use bar muffs? hear a few guys on here have them push back into the front brake at higher speeds

I understand where you're coming from, Max but it's a 42,000 mile bike used 4 days a week/200 miles a week. It gets warm enough.
Quick Question, is there a fuel filter in the tank on the Ten?

HT coil came in on spec for resistance on primary and secondary windings.
Valves, inlet were slightly loose on one, exhaust was slightly tight on both.
Guess we'll see what tomorrow brings. For reference on the 25 mile ride back not going above 4000 rpm it was faultless.

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