ORIGINAL: JohnBuckner
My personal reccomendation is to avoid any third line as it is actually redundant and unnesesary.
Disagree. Without a third "fill line", you must T into the engine feed/clunk line. This works fine, of course, but I have had some issues with flooding while doing that. Unless you can block/pinch the line between the T and the carburetor, fuel will get to the carburetor during filling.
This is not an issue with most engines, I know. But it was a problem with my Laser 150 on two different airplanes. And yes, the carb rotor was closed. Didn't matter; the fuel was there, waiting and under some pressure, so when I cracked the throttle for starting trim, it poured in there and flooded the engine. Of course, the Laser has its carb in an odd place; but still...
Another option is one of the fuel filler jobs with no moving parts; when you insert the fueling probe, it blocks off the route to the carb. The Sullivan unit is an example, but it is a bit too big for a small airplane, IMO. I use this on my larger models.
I agree heartily that the "fuel valves", as extant in the DuBro and Hobbico units, are problems waiting to occur. In addition to the dirt/grunge issue already mentioned, the small probes are easy to misplace; and then you're done.
So, yes, there are better ways to skin this cat than a third fill line. But it is still a viable method.
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