Rotax 503 has me baffeled.

[Methusala]

I have discovered that the black valve material in the choke plungers may crack over time. I know that the chokes are "enrichers" and should only bleed fuel when the throttle slide is shut. Never the less it is something to be aware of on Bing carbies. Don. (And by the way have a happy, family friendly and safe holiday.)