idle drops after starting when warm

Here goes...when cold bike starts first time. With fast idle out it'll run fine for about 10-20 seconds then the idle will gradually drop off and the engine will chug away until it stalls (unless I give it gas). If it stalls & I start it up it will run perfectly with absolutely no hiccups or idle problems when stopped or moving.

However, if I stop for a short period, say to grab some groceries, she'll fire it up first time and the above problem will occur. If I pull away the engine can feel slightly rough as if firing on 1 cylinder with the odd lurch then everything is back to normal.

I should point out that the fast idle doesn't pull out as far as it should, so that might be the reason it happens when cold but I have no idea why it happens when warm.

i had a problem with this a few weeks ago and was found to be an HT lead was a nuisance because only happened now and again.. i found by chance after a run spark was arcing all over place and garage was dark was like a strobe light.. i picked up a set of leads and plugs from Motorworks bloody expensive set of rubber at that.. problem solved and now runs great.. only one solution Denny plenty pending....

It's not stopping me from riding and doesn't seem to be getting worst, so business as usual then I suppose.