Engine Missfire

[rossoandy]

Hi folks, looking for some thought on this one. Its real difficult to explain but I do my best.

2000 Rosso Mandello.

This bike has always impressed me with its ability to run down to very low rpm without judder or apparent distress and then pull away cleanly and strongly. I realise that i am asking a lot to run as low as 1200rpm and then with a whif of gas glide away but thats wat its always done. Things have changed! Now it feels like its missing at low rpm,its not running on one cylinder as such but something is not right. Its so difficult to explain, its more of a feeling...

Three times in one day I stalled the bike pulling away, wheras it used to pull away virtually with no gas at all now you need to rev a little and slip the clutch. It feels although its missing its very low down torque. And yet I cant say it missfires that you can hear or feel as a vibration.

My thoughts so far are..a partially blockd injector nozzle...a dirty air filter, an air leak on the inlet rubbers, a tight valve..an ignition coil failing-low on kv.perhaps some dirt on the timing pick up? I really dont know where to look first!!

Incidentally I have changed the spark plugs.

When revs pick up over say 2000rpm all feels as normal and performance is strong otherwise.

So guys, your thoughts please....I am a qualified car mechanic so have some idea wat I am on about but this puzzles me at the moment.

i intend to start with the tappet clearances as I never checked them!

Then the air filter next and I guess while there a fuel filter would not do any harm at 12000miles.

Incidentally I also feel a coarseness through the footrests on a neatral throttle but feel this a different problem on its way!

[jrt]

Look at the easy stuff first, then move on to the harder bits. Check the intake boots for cracks, check valves fer chrissakes- it takes 20 minutes and a beer. Make up names for the parts and impress your girlfriend. Check your plug gap (again) for that matter. Changing out the air and fuel filters is more involved, and being as lazy as I am, I would check those later. Coil or crank pickup are unlikely and catastrophic when they fail, so put them on the late list. Also- it kind of sounds like your throttle bodies could be a bit out of synch. Do you have a vacuum gauge to check that? It's pretty easy.