Bike ran okay 'till it was laid up for a few months, (nearer a year), and then it would only run with the choke on. Suspect idle circuit? Stripped and cleaned carb, some gunge around the needle valve was only problem found. Still wouldn't run with the choke off. Inspected fuel tap and found it partially blocked and rubber parts disintegrating. Bought a pattern replacement tap, cleaned out tank and tested with fresh fuel - new tap functioning perfectly in all 3 positions. Engine will still only run on choke. Stripped, cleaned and inspected carb again and checked float level. Would still only run with choke on. Had carb ultrasonically cleaned - no difference, still will only start and run with choke on. Tried tuning the mixture screw on the carb from the 1 1/2 turns out base setting as recommended by the manual and fiddling with the slide stop. Which I admit is not going to achieve a lot with the choke on, but I'm running out of options and am willing to try anything. With the bike running, (with the choke on), any attempt to lower the choke lever results in the engine 'dying'. But if I grab a handful of throttle as I lower the choke lever and hold it at around half throttle the engine revs up okay and will run at that speed until I back it off and the engine dies again. I would think that this shows that the problem is with the idle circuit? However the jets and carb drillings are all clear and besides having the carb ultrasonically cleaned and blowing through all of the orifices several times with a high pressure air line - the damn thing will still not run with the choke off. Any ideas would be welcome and appreciated.