nosram,

As with anything, opinions vary. For every person (like me) who says he had grief with those miserable fueling valves, a half -dozen guys will pipe up with "I've used those for years with no problems".

I tried two different Dubros, and have watched many modelers struggling with both Dubro and the GP version. All did the same thing as yours; the valve sticks, either open or closed. Personally, I think it is a problem with the tiny O-ring in there.

So what to do on a cowled engine? Either use a YS, which can be direct-fueled without fear of flooding out the carburetor, or do like I had to do on my Horizon 73" CAP/Saito 150 combo; use T-adapters, which routes the fill line outside the cowl where you can get to it (fuel dot) and pinch off the feed line between the T and the carburetor with a hemostat to keep from flooding the carb while filling the tank.