Gas cap experimentation happened today... This has been bugging me for a while, so I finally took action. Hopefully something worthwhile-ish
10 series gas cap; duck bill had turned to goo, but when trying to get it apart (all plastic, not the brass center) it all crumbled, including the middle "tube" that is part of the gas cap. JBWeld to the rescue!
First I cut down the center tube with a 3/4" forstner, and then poked a wire through the vent hole (coated with oil) hoping that the JBWeld I was going to "pour" in there wouldn't stick. That mostly worked, and JBWeld flows reasonably well on a nice hot summer day and the wire maintained the hole with minimal grief removing it. Grease would probably be better than oil next time.
This is (was) a brass plug I picked up at the big box while contemplating this project one day. I drilled it out all the way through with a 5/32 to fit a duckbill (i think "poulan"? just because I had some) and then drilled it again with 13/64, but not all the way through. This left a seat of sorts for the duckbill, so it would push through and seal (hopefully).
Back to the JBWeld filled cap... That got drilled out with a 3/16 and then tapped. The spring is actually a meter lever spring that I stretched out over a drift (both length and width). Not ideal, but it works until I can find something better. The JBWeld is perfect, because it's hard enough to hold threads, but soft enough that it seals the brass plug when threaded in. I also drilled a little pocket in there for the spring to sit in.
So far, so good... I have yet to field test this, but it doesn't dribble gas out the top of the cap any more! Still need to see how this goes though... might drill out the smaller hole in the brass to 11/64th - it really needs to be between 5/32 and 11/64 I think, but we'll see. 5/32 is kinda snug, and I'm afraid 11/64 will be too loose around the duckbill. Also need to find a better spring option. Anyway, as I said, it doesn't leak gas out the vent hole now when turned upside down, and the spring action should allow tank pressure to blow off before it forces the carb needle off it's seat. That spring is kinda weak though, so hopefully it keeps the duckbill seated after pressure blows off.
On the upside, now it's serviceable again, and that JBWeld will outlive the cap.
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