Fine on the way out , on return journey bike started to run rough, wont idle { nothing new} running on one cylinder until you get to 3k then picks up like nothings wrong. Took it out on the motorway 70 + for 10 miles, pull over for an hour , start it up and idles rough then stalls. Start it up...one cylinder again for 1.5 miles on A road full throttle in 2nd 40 mph max, throttle off then 2nd pot picks up?
Pulled out rear plug , oh wot fun, plug looks like its running lean fan is on nearly all the time.
Any ideas ?

Trade it for a tuber

_________________
Mithered ta death.
92 MB
96 S2T
98 S1W
00 M2
01 X1
03 P3
10 CR

And in the meantime?

Blink, pulling a plug and looking at it will tell you very little about the mixture. To do a 'plug chop' requires a very specific procedure and modern fuels don't give clues like the old leaded stuff did. Even if you take a trip to your nearest airfield and fill with leaded petrol, modern FI and Cats really don't like the stuff.
You'll need to spend time on a Dyno to sort fuelling.

_________________
If your dreams don't scare you, they are not big enough.

HT lead worn through? Do a search. Common issue...

Rear cylinder should never run lean as the lambda sensor controls closed loop from there. Any fault codes stored (check the how to section)?

_________________
08 Specialized Langster

Thanks Adam,
i must be getting old , teknolagy is a .
Maybe i should just get the bus

Pash lead looked OK, lots of oil from airbox so took HT lead out so i could mop up ,

Lots of oil in airbox??

Check your oil level.

Please explain how an excessive oil level in a dry sumped engine would result in the breathers dumping into the airbox ?

_________________
Mithered ta death.
92 MB
96 S2T
98 S1W
00 M2
01 X1
03 P3
10 CR

No no no .......lets work out why my piece of shit Uly is fucking rubbish, sorry i mean firing on one cylinder.

Could be one of many known issues which are all easy enough to diagnose if you know what ya doing and have the right equipment.

I'll kick off with a faulty ign. coil ?

_________________
Mithered ta death.
92 MB
96 S2T
98 S1W
00 M2
01 X1
03 P3
10 CR

What year bike Bink and how many miles done. Any mods on it.

06 bike 4700 miles no mods,

Checked the earth lead under the seat ?

_________________
'08 Street Triple R
'07 XB12 STT (now gone)
'03 Vauxhall VX220
"is it meant to do that ?"

Done that today, no difference. Ordered some plugs and leads will try these first then replace the coil if no result. Shit loads of oil in the airbox again...only cleaned it out 40 miles ago?

If you have lots of oil in the airbox then it is going to go into the engine with the burn cycle and could foul the plugs. You should have none of note.

It sounds like you will need to seek advice from someone like Maz on this issue.