Random thought time.
How do you start the bike? By this I mean do you twist the throttle as you do it?
It may be that your idle circuit is not working, but you're twisting the throttle enough for the motor to catch, but then releasing it and closing off the extra air / fuel...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
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GTS1000 oddball