Fuelling / Engine trouble on CBR - (longish)

Been having some issues with poor running at low speed while the
engine was warming up (bike shaking so much it felt more like a
bronco) during a couple of the recent cold mornings. Once warmed up
though it was generally fine, but with a service due, I thought it
would be a good time to check plugs and filter.

Got the tank off (as per Haynes manual), and checked the air filter,
seemed dirty, but not too bad, so I put it back in (reconnecting the
tank and all the hoses). Same with the plugs, not perfect, adjusted
some of the gaps (ever so slightly), a little too much carbon, but
nothing too extreme. Put everything back together again, put back
fairing. Feeling rather pleased with myself I went for a test ride.
Felt a bit lumpy at first - nothing unexpected here as nothing had
been changed, but instead of improving, things got much worse leading
to a stalled bike. Finally got going again, but needed plenty of gas,
and the engine was extremely lumpy.

I have since swapped out the air filter for a new (OEM
Honda)(improvement but still nowhere near what it should be), and the
plugs - even checking the torque settings with next to no difference.
Additional info:

- Plugs appear to get soiled with fuel
- Lingering smell of petrol (no surprises)
- All downpipes are getting hot so I do not believe I'm having trouble
with cylinders.
- Bike will 'run' but has small backfires at low revs (<3000), is
'lumpy', and has no power when given some beans.

Any suggestions on what to check next?

 

"Ginge" replied to a plea for help

Would definitely agree, sounds like it could be the carb jets that are
getting blocked, be worth double checking the fuel filter, whether that's
inline on your bike or in the carb I don't know, im working from experience
on a scooter after all

Otherwise the only other thing that springs to mind is electrical i.e.
cracked or worn spark plug caps or ht leads, is a possibility, hell the
thing might even be earthing somewhere? Ive known this happen on a lammy,
was detected by starting it up in the pitch black, you could see the HT lead
sparking and earthing to the frame and exhaust.

Its possibly but my moneys on a partially blocked carb jet

 

Ginge wrote in message:

You've all pretty much summed up how I felt this afternoon, so I
dropped it off Lloyd Coopers.

Whilst I've enjoyed getting to know more about my bike, the most
valuable lesson I've learnt is not to fucking touch it. Still, plugs
and filter - what could possibly go wrong?

 

I've occasionally cured problems like this by draining the float
bowls of old, rusty water. Tho' where anybody'd get water in their
carbs in this recent weather is a mystery! Also check no breather lines
were pinched when moving the petrol tank, etc.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Room 40-1-B12, CERN
GSX600F, RG250WD. "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Bingo! Ignition coils incorrectly connected to the cylinders. How I
managed to **** that up with 4 cables is anyone's guess - memory ain't
what it used to be (should try proper labelling in future). At least
the rest of my work has been vindicated.

Bike's ready for pick up at the same time my mate picks up a nice
shiny brand new ZX9R.