Hi,
Having trouble with my ZX9R B4, I've had it running sweetly in the car before but after taking it out to do some other work it no longer runs without the choke being out.

I start it from cold with the choke out but after I've let it warm up I cannot take the choke off with it stalling. Also it wont rev without cutting out, as soon as I try a little throttle it just dies.

I removed the plugs and they were very black and possible wet?

It has also has a dynojet kit fitted.

Any clues please?

air leak ?

Mine (c1) was reluctant to tick over without choke until I dynojetted it. I too have similar plugs until I can get it tuned properly. What jets and needle settings are you running?

check the float chambers aren't all gunked up. I had exactly the same when we forst installed the zx9. I've got all the details on my website, but its disappeared :-(

Yes, ZX9R carbs are sensitive to dirt / gunk etc according to the biker forums

The 9R carb 'chokes' are really fuel enrichment devices, they don't choke the venturi as in say a downdraught weber.

That said it sounds as though the main and / or pilot jets have got gunked up during the engines lay off, and using the choke richens the mixture up enough to allow the engine to run.

A carb strip and clean out should be 1st on your list of jobs.

As already stated, I would start with a strip cleaning all the carbs!

Hang on a minute.....

Something's wonky here (or maybe just my logic!)...

If the plugs are sooted it indicates it running really rich. But.... the engine will only run if the chokes is out (ie even more fuel).
why would an engine that previously ran okay only now run when ridiculously rich??

Benb,
Your right its a bit confusing, wondering if the plugs are wet/black because I've only ran it on fully choke for the last few 'testing' runs. It needs to be rich to run but the choke has made it too rich and foweled the plugs.

But you all correct I should clean the carbs first and see what happends. It was a job I was trying to avoid but I know it makes sense now....of to Halfords for some carb cleaner then!