Slicing off the filler spout?

[Gcraay]

I have an old Triumph gas tank I'm wanting to use for my build. I want to how ever change the cap. It would mean slicing off the factory filler spout and then installing my new low profile cap.
Issue 1. The existing hole is just a hair to big. I mean just a hair really.
issue 2. The new part is aluminum, and the tank is steel.

Any advice before I slice?

This is the style tank.

 

[MaxPete]

Well, welding aluminium to steel is possible, but it's not easy, and I wouldn't trust that sort of weld on a fuel tank that is situated,,,well, you know....where a motorcycle fuel tank is normally located.

Could you bond (glue) an aluminium plate with the correct sized hole in it overtop of the hole in the steel tank and attach the cap to that plate? Then just fair-in the seam with body filler in the usual way.
There are lots of types of glue that should work for that I would think.

Pete

 

[fredintoon]

I have an old Triumph gas tank I'm wanting to use for my build. I want to how ever change the cap. It would mean slicing off the factory filler spout and then installing my new low profile cap.
Issue 1. The existing hole is just a hair to big. I mean just a hair really.
issue 2. The new part is aluminum, and the tank is steel.
Any advice before I slice? View attachment 92569
This is the style tank.

Hi Gcraay,
I'd advise you don't slice up that Triumph tank, it's a scarce item that's worth a fair amount of money if it's left alone.
But if you are bound and determined to cut it, here's what I'd do.
Cut out the filler spigot to leave a BIG round or square (you choose which) hole.
Carefully save the cut out piece so it's possible to weld it back in and salvage the tank with it if your plans change sometime.
Weld in a depressed rectangular or circular steel well with a hole in it that'll accept your aftermarket filler cap.
Note that the Yamaha XS1100 Standard has a depressed flushmount filler cap.
It's cap depression has a drain tube that runs through the tank to let rain or spilled gas drain out.
You can do that too or always carry a towel to mop up with.