Bike problems here...any ideas most welcome...lady in
distress needs some help! 

I have a 96 ZZR1100, but all of a sudden she has stared
playing up?  It seems that over night she is delivering
exceptionally poor performance at low end.  Anything above 3k revs
she's good, anything below that she's coughing and spluttering and cutting out
all over the place.

So far I have given her a sip of Redox, no
change....Stripped her down, gave the jets and everything else in the
vicinity a jolly old blast of squirty cleany stuff....put it all back together
with new gaskets...took her out,no change!...spark plugs look good and firing
well, so no its not that....

I "borrowed" a coil off my mates bike, fitted
that...took her out, no change....the only thing I have not tried to my
knowledge is to change the HT leads...after that I have I ran out of ideas
completely!

Someone suggested colour tuning the spark plugs, but to
be honest I don't think that would make a huge difference really and its a
major pain to do anyway....ho hum I will not be beaten by a bike!! grrr....any
suggestions that solve this I will take you out to dinner.......Gabrielle x

                                                                                                                                                                             

Vacuum operated fuel tap? - bad diaphragm or hose not allowing the tap to open properly?                                                                                                                                                                             

I checked each diaphragm and they were all in good condition and seemed to move smoothly....and they located in the rims ok...                                                                                                                                                                             

Get the valve clearances checked - I had similar issues - bike would randomly cut out at low revs - turned out the exhaust valves were very, very tight - often it's the inlet side that's tightened over time - so get them done and you should notice a huge difference                                                                                                                                                                               

Nah - I meant the diaphragm in the fuel tap itself if you have that type? Try riding with the tap set on reserve? If that imporoves things then your problem is in that area.                                                                                                                                                                              

Cool thanks Richard, I will try that next...that's an easy one to rule out.                                                                                                                                                                               

Hi, 
When the spark plugs are tested outside the engine you will get a good spark. But in the engine it could be a weak spark due to too much resistance and the spark going elsewhere rather than the chamber.
Poor battery, HT leads, spark plug cap and plug resistance are not correct,
Pick-up coil wrong resistance.

Pilot screw maladjusted, floats in the float bowl need adjusting. air bleed pipes blocked. fuel tank air vent blocked.

Compression low.

More likely to be the electrics or fuel. 
Hope this helps.

                                                                                                                                                                             

Thanks thediver37, I see you are covering all bases!  lol   No, really its much appreciated.  Gives me plenty of food for thought....

Cheers,

Gabrielle x

PS - Nice pics btw.
                                                                                                                                                                             

Sorry - wrong wording - I meant try with the fuel tap in the PRIME position, if it has one? For ON and RESERVE a vacuum connection from one of the carbs is needed to make the tap open. On PRIME it's pushed open mechanically.

On the other hand, just re-read your original post and if you're running OK at high revs it's unlikely to be fuel supply.

Is it OK starting? Could be battery or regulator problem if not getting enough current to the coils at low revs.

Mate had running probs similar to this, turned out to be leaking exhaust from header gasket and small rust hole in collector, he fixed these and it ran better , also found that idle adjuster had been ham fisted and spring stretched at some point, after fixing and final tick over carb balance it ran ok, this was a zzr6 though

Ok, after reading through these posts about the problem I think it is one one of two possibilities, there`s a clue in that it runs ok above 3k.

You either have a blocked or restricted pilot circuit in one or more carbs or there is a fault in the CDI unit.
The CDI box basically has 2 timing speeds: the first is for low speed running & will operate up to about the range you`re saying before the 2nd kicks in & takes over. This may be why it feels ok above 3k. To test this you will have to makes friends with another ZZR rider & borrow their CDI to see if it cures it. Check the part number on it to make sure it matches.

Thank you guys....all good stuff.

I have ordered some new needle jets, I think two of them are iffy and not closing the valves, hence flooding carbs on 2 and 4 and performing poorly at low end??  but I wont know if that's fixed the fault until they arrive...I hope it does, but I will  have to start looking at other stuff if it doesn't. 

Gabby x

I had badly worn needle jets once (see pic, old & new)
http://i9.photobucket.com/albums/a54/RichardT/Tech%20stuff/P1010446.jpg

Rich running and drank fuel, but kept going!
                                                                                                                                                                             

Problem solved...not so poorly ZZR11 now, new needle valves did the trick.  I'm now back on two wheels!  yay! 

Thanks for all your help and support you lovely people...Gx
                                                                                                                                                                             

just read all that and you have done it, wow I'd have said slow running side as well. when carbs are stripped also worth blowing  the pilot holes and galleries throughh with compressed air. So now your running will have to join you sometime on a run out.