Replacing Gas Cap on Fiberglass Tank

Big Red · Aug 23, 2022

I am planning on replacing the gas cap on my 71 750 with fiberglass tank, but concerned about how a 51 year old fiberglass tank will hold up to drifting out the pin. Anyone have any advice on this? thanks!

B+Bogus · Aug 23, 2022

From personal experience they're no more - or less - difficult than for a steel tank.
The important thing is to have the cap well supported while you drift the roll pin out

baz · Aug 23, 2022

Use a parallel pin punch that fits the roll pin perfectly with a flat end
Don't use a centre punch or anything pointed

Stephen Hill · Aug 23, 2022

A FIBERGLASS TANK! AAAARRRGGG!!!
DRIVE OVER IT WITH AN EXCAVATOR THEN RUN AROUND WITH YOUR HAIR ON FIRE.
Just kidding.

Craig · Aug 23, 2022

Like Baz , not difficult , if corrosion present use some spray oil WD40 , penetrate something then come back to it , I did it with no damage or problem so pretty well anyone on here can …. Yup on FG tank ….

Tornado · Aug 23, 2022

Be sure to place a bit of cardboard/rubber mat etc around cap where you need swing the hammer to try to protect paint work.

Btw, if you are to re-furb the cap, be sure to not just replace gasket. Remove the spring supported plate to swap out original, likely brittle/crumbly bit of rubber hose with modern ethanol resistance hose. It is this hose that provides the sealing force against the tank neck, not the metal spring. Some caps have a rivet holding the plate, need to be drilled out then run a tap through and use a machine screw (or re-rivet).

baz · Aug 23, 2022

Tornado said:
Be sure to place a bit of cardboard/rubber mat etc around cap where you need swing the hammer to try to protect paint work.

Btw, if you are to re-furb the cap, be sure to not just replace gasket. Remove the spring supported plate to swap out original, likely brittle/crumbly bit of rubber hose with modern ethanol resistance hose. It is this hose that provides the sealing force against the tank neck, not the metal spring. Some caps have a rivet holding the plate, need to be drilled out then run a tap through and use a machine screw (or re-rivet).

Yes I remember you doing a very good post about that

Craig · Aug 23, 2022

Geez Torry , I sure don’t remember swinging a hammer during this job , think I just tapped with hammer , some protection can’t hurt ! But avoid any round house swings , this stuff is old ….

Tornado · Aug 23, 2022

baz said:
Yes I remember you doing a very good post about that

See, I'm not just another pretty face... ; -)

Big Red · Aug 23, 2022

Thank you gentlemen, very good advice. Will give it a go.

Tornado · Aug 23, 2022

After recently mangling a roll pin trying to drift with a standard drift punch, I came across this roll pin drift set. If you look carefully, there is a shoulder to seat into the pin end, squaring everything up. Worked very well.

Cuppy · Aug 24, 2022

Stephen Hill said:
A FIBERGLASS TANK! AAAARRRGGG!!!
DRIVE OVER IT WITH AN EXCAVATOR THEN RUN AROUND WITH YOUR HAIR ON FIRE.
Just kidding.

Just do not use fuel containing ethanol.

ILLF8ED · Aug 26, 2022

Cuppy said:
Just do not use fuel containing ethanol.

I agree and even with a steel tank I cannot leave ethanol laced fuel in the carb bowls very long without the jets getting fouled.

Replacing Gas Cap on Fiberglass Tank

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