Rough, rough running

[craigie]

My wee bike is running rough as **** when I try to go fast, if I pootle along it's not too bad but if I twist the throttle hard it starts a kind of staccato misfiring and losing power. It happens all the way through the rev range. I have changed the fuel filter and air filter and cleaned the plugs which admittedly don't look fantastic. When I changed the air filter things seemed to get worse. I changed it because the last one was a bit burnt from a bout of backfiring a while ago which was cured with new(ish) coils.
I'm thinking, in my non mechanical mind, that maybe the bike had made a free flowing filter on its own and now that it has a non burnt (standard) one that not enough air is getting in the mix and making the bike run rich and therefore fouling the plugs. Does that make sense or am I way off track.

[slob]

then the plugs should be black rather than a grey/light 'biscuity' brown colour

[craigie]

They are a kind of dark biscuity colour, what does that mean?

[slob]

that's probably ok, gey/tan/brown is good
http://www.mkiv.com/techarticles/read_plug/plugdiag.jpg

[craigie]

Cheers for that man, very handy, the insulator is a bit discoloured so I'm thinking High Speed Glazing...whatever I guess Ray will be getting a visit tomorrow evening.

[manwithredbike]

just a thought - carb icing (if its a carbie). has it been fairly cold/damp since it started misfiring?

[slob]

It's also been wet and horrible, check for signs of scorching on the outside of the front plug, around the plug cap. That can cause problems however your new set of plugs should have fixed that.

[craigie]

Changed the plugs and put a free flow filter on and....absolutely no difference, rougher than ever today before I changed the plugs and just as bad after.
Any ideas anyone?

[dam]

just a thought - carb icing (if its a carbie). has it been fairly cold/damp since it started misfiring?

What he says

[craigie]

What he says

It's not what he says. Cheers though.

[Matt Tracey]

Did you get this sorted?

My bike is doing exactly the same thing - almost feels as if its dropping onto one cylinder and only happens when the bike is warmed up in wet conditions.

Thought a service would sort it, but its just had a major service at Aylesbury Ducati and its worse than ever!!

[craigie]

So long ago and so many problems since I can't quite remember what fixed it. I do know that getting the valves on the front cylinder properly adjusted made a big difference, the guides or something...also had a new bit of loom and so many other things since.
Sorry that this is probably not the definitive answer that you had hoped for. Good luck though, hope you get it sorted.

[Matt Tracey]

Thanks - I think a visit to Rosso Corse beckons!!

[craigie]

I have no experience of Aylesbury Ducati but have not heard many positives about their servicing. Rosso's definitely a better option.

[benson]

Would heartily recommend Rosso COrse - mine was behaving similarly last year - dropped onto one cylinder eventually as I was leaving the M25...interesting experience - needless to say Ray fixed it.

[Gamsa]

Sounds like a fueling issue to me. Benson, what was the diagnosis for your problems in the end? I've just changed the jets, needle and emulsion tubes in mine to dynojets and it made a world of difference. That was from running standard jetting with a cut off airbox and aftermarket exhaust, though, which was clearly a mistake by the previous owner. The emulsion tubes do wear oval which causes fuelling problems. What's the mileage on the bike? Could also be blocked jets or a split diaphragm. If it were me, I'd have the carbs off.

[benson]

Fuelling it was - and buggered plugs and a lot of running in really crap weather.....

[benson]

Oh and it was about a year ago!!!!