major running problem. Suggestions needed

I took my curvey out for a 60 mile round trip the other day and for the whole of the outward journey it felt very flat, was unhappy ticking over and needed coaxing to re-start if it stalled.
Come the return journey, it needed full choke to start, even though I'd only been stopped for about ten minutes, and for the first couple of miles would only run on one-and-a-half cylinders. Once it stopped doing that it popped and banged through the exhaust every time I shut the throttle and when I got to a stretch of open dual carriageway I found it no longer had enough power to pull top gear. By the time I got home it wouldnt pull anything higher than third gear and was overheating so much I could smell it at 30mph, which was pretty much maximum speed by then.
I was convinced one of the chokes had jammed but neither had. Nor had either of the air screws unwound itself nor the diaphragms split.
More in hope than expectation, I replaced the spark plugs, put it back together again and was astonished when it started first prod of the button and appeared to run normally. It was only when it started to warm up that I discovered that all it will do now is run on full choke when stone cold. Back the choke off as it starts to warm up or apply even the tiniest hint of throttle and it instantly splutters and dies.
I've now run out of ideas.
HELP!!!

Might be worth having a look at your coil resistance and the electrical connections to the CDI.

At the minute, I can't think of anything else. Hopefully someone else with greater technical knowledge than I will be along shortly!!!

That was suggested by a bloke at work, but the evidence points so much in the direction of a carburation problem I'm not convinced (In any case, he rides a Kawasaki so is not worth taking seriously)

PS. How much humble pie will I have to eat if it does turn out to be an ignition problem?

Originally Posted by mikemm

PS. How much humble pie will I have to eat if it does turn out to be an ignition problem?

I'm after some Ohlins springs, so you could buy me some of them if you like?

>>and was overheating so much I could smell it at 30mph, which was pretty much maximum speed by then<<

What could you smell ? petrol - coolant ?
Did your overtemp (the red LED on the clocks) light come on ?
I would also suspect carouration in the first instance, but I'd also check your coolant levels (I used to have an MGF, so was quite used to coolant smells).
Check your oil etc.
Is the bike modified ?

It was the kind of smell you get when you've been caning it really hard - mostly hot metal. Oil and coolant levels checked seconds ago and found to be exactly where they ought to be.

One day I'll learn to answer peoples questions in one go, rather than in installments.
I dont think the temperate light works. Certainly I've never seen it on, even when I first turn the key and all the other idiot lights come to let you know they're working. Is it supposed to do that?
The bike is not quite standard, having had BMC filters throughout the two and a half years I've had the bike and a Quill T3 street pipe for the last year and a bit.
I should also add that this bike has a history of carburation problems. Just a few hundred miles ago, for instance, I had to chug it 60-odd miles back from London on one and a half cylinders. I was then convinced a choke had jammed but it turned out to be an air screw that had unwound itself a remarkably long way in an extremely short space of time. That is why they are the first things I checked.

Have you checked all the fuel lines to your carbs? Perhaps your bike is running too lean and that's why it only runs with the choke open fully seen as you're running a different filter?

A fuel blockage was another of the Kawasaki rider's suggestions and has been checked and found to be okay.