Topic: '78 750F with plugged gas cap

[superchode]

found a few posts in the archives about other years... but from the descriptions of how to fix it, i think the '78 cap i've got is slightly different.

the hole in the top of the cap is clear... but i don't know where it vents to in the base or sides of the cap.

where is the air path? and what's the best way to get this thing breathing again?

[Lumbee]

...my 550 had a plugged cap, and everything was clear as far is I could see, but still wan't allowing air like it should.  I ended up taking the smallest drill bit I have and just drilling a big fat hole in the bottom of the cap...

[superchode]

so the air flow is right through the base of the cap? there must be some sort of hole underneath the piece that the cap-retainer chain hooks onto. i can poke around under there... the top of the cap certainly doesn't have any blockages.

[Lumbee]

hmm...the 78 tanks also have a tube/nipple on the under side of the tank that opens to the air...make sure that one isn't clogged either.  I'm sure its simple, but I don't know all the vent paths on the tank.  U'r right, theres the one in the top of the cap, but theres also the one on the under side too.  How are you checking to see if its venting or not?

[theunrulychef]

hmm...the 78 tanks also have a tube/nipple on the under side of the tank that opens to the air...make sure that one isn't clogged either.  I'm sure its simple, but I don't know all the vent paths on the tank.  U'r right, theres the one in the top of the cap, but theres also the one on the under side too.  How are you checking to see if its venting or not?

That's just a tube to allow rain to drain from the indent in the tank as far as I know. 

Have you tried blowing compressed air through it?  Might also try pulling the gasket off & soaking it in some laquer thinner.

One thing I can tell you not to do from my previous stupidity is to not glass blast the cap - got the carbies full of tiny glass beads that way.

-Jay in Philly

[superchode]

well, i know it's clogged since the fuel only flows for a few seconds if the cap's locked on... cracking the cap allows the fuel to flow again.

i've also put my mouth over the top hole in the cap and blown.... nothing got through. i could try hitting it with compressed air.. would be pretty hard to seal the tiny hole in the top of the cap to make it effective.

it was clear a few days ago... it's been subjected to paint on its top side and phosphoric acid on its bottome side since then.

[jtb]

Chode,
I've got an extra cap laying around.  Ya want it?
John