Gas Cap rubber tube inside spring?

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Roadnwater

Roadnwater

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The gas caps for Commandos have a rigid rubber tube about 1/2" long that fits inside the spring. On the replacement cap this does not compress and there is no way to get the cap down enough to latch. I removed it and the cap still seems to seal well with the spring force alone. Question is what is the purpose of this thing so I know that it is OK to leave it out.
 
The thin rubber disc seals only to the tank neck.
The "flexible" rubber tube is the seal for the center column positioning the disc.
With no rubber tube seal, the tank can still splash liquid on through and wreck the paint.
The residual functional "vent" is the tiny holes in the steel discs and are each on opposing sides.
Especially bad when using E10...turns rubber into a rock
 
Thanks for the explanation and I see now how that tube works. I purchased the new cap a long time ago and I guess that the rubber has hardened even without use. It is pliable but there is no way to compress it from the end direction. I will try to find some tubing that will work.
 
I restored my original cap when it was leaking by drilling out the central rivet and replacing the nearly solid rubber with afresh pliable bit of fuel line. Tapped a thread where rivet was and just used a bolt and washer. Immediately solved the leaking.
 
My replacement cap has the screw already. I was wondering what type of tube to get and your tip to use fuel hose is very helpful. I am off to find some.
 
Gas Cap rubber tube inside spring?
 
Thanks everyone. Got fuel hose from local real motorcycle shop that still has rolls of such by the foot. I cut it shorter than the rubber one that came with it but enough to seal when cap is closed. Now I have to install the cap to the tank with the ******* pound in pin.
 
Roadnwater said:
Thanks everyone. Got fuel hose from local real motorcycle shop that still has rolls of such by the foot. I cut it shorter than the rubber one that came with it but enough to seal when cap is closed. Now I have to install the cap to the tank with the ******* pound in pin.
Click to expand...
Use a proper parrelell pin punch to put the roll pin in if you can
Cheers
 
tape up the tank real well, once hammer bounce into the paint is all it takes:eek:
 
I used a a suitably sized drift and long enough to have the striking end well clear from the tank. Used a thick rag around filler neck area to further protect my preciously new paint work. Worked great.

Before placing cap onto tank. be very sure you've got enough sealing force from the new bit of hose....you should need to push down on the lid with quite a bit of force to get it to clamp onto neck...that's your sealing force on the flat rubber seal. You can test fit before fitting the pin. Also once done. keep a close eye on the neck area/surrounding tank once filled with fuel...I only noticed my original leak when fully fueled after a bit of corning work and happening to notice the tank side was wet.
 
Got cap on but nerve wracking with original paint on tank. I drilled a hole the same diameter as the pin in the end of a bolt about a 1/4 inch deep. That prevented the "drift" from slipping off the pin. When it was almost all the way in I had to use a regular punch for the last bit. Thanks for all the advice.
 
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