My Tank is giving me a headache

TezazGuzzi88

New Member
Customizing a Mark 5 Moto Guzzi and the tank filler cap mod is proving to be a little headache.
Cant seem to stop procrastinating on how to fit the new style filler. I am thinking of making the cut a round shape like the filler then straight and narrow to fit the cutout of the old piece Some bending and shaping needed here to. How have others on here tackled this.
Not looking at an aluminum replacement tank.



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gt alex

Been Around the Block
To me it looks like it just fits across the stock recess I would cut a peace of flat plate to size mark drill and attach the inside nuts then weld/braze the plate in place and then cut the filer hole. I think it has more chance of warping out of shape if you cut the hole first.
I think tightening the cap in place will pull the tank to a god shape.
I'm just going buy the pictures and I'm not familiar with that type of cap so does that make sense to you?
 

TezazGuzzi88

New Member
The cap sits flush without a recess so the hole and fittment need to be done first.


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TezazGuzzi88

New Member
Actually there is a plate that fits underneath so I qas expectingbto use that but perhaps I can tig the nuts on before making the hole. There is also a cork gasket which provides a seal

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teazer

Over 1,000 Posts
DTT BOTM WINNER
Assuming that you want the filler cap to be more or less flush ie recessed, it's good news is that the filler cap fits into the recess. So you need the mounting flange to be at the same depth, and you need the rest of teh filler panel to be level with the top surface of the tank. That means the new panel has to be stamped/bent to have the correct recess.

What I have done on a couple of tanks is to but a smashed tank with caved in sides but a good top. That way I cut out the top around the filler cap and modify that until it can be welded into the new home. That way, I get the drain and breather tubes as well with any luck.

Distortion will be your biggest worry (well it was with my crappy welding) but if you can weld, just take your time.

If that is all too much, you could also just "fill" the stock recess with that piece of sheet steel, and leave the filler cap sitting up above the tank surface. It won't look quite as smooth, but I doubt that anyone else will even notice. Cut the filler piece to the same size as the existing rcess if possible to that the tank retains some of the original curves on the top. If you cut it all the way out to that marked line you will end up with a large ugly flat suface.

If you had an English wheel you might be able to stretch the filler panel to match the original curves, but that's above my pay grade.
 

TezazGuzzi88

New Member
Yeah I want to just use the existing recess as much as possible drilling the hole after never really occured to me. Might be an option now.
No english wheel or anything like that as this may well be my one and only project .
I was thinking of shaping the steel to fit then re drilling the hole.
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doc_rot

Oh the usual... I bowl, I drive around...
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It will help if you can get some dimension in the piece to minimize warping since you will not be able to work the metal with a hammer and dolly after the piece is filled in. I would make a hammer form. the better the fit up the less warpage. you'd be surprise what you can accomplish with hand tools and a lot of patience.
 

TezazGuzzi88

New Member
It will help if you can get some dimension in the piece to minimize warping since you will not be able to work the metal with a hammer and dolly after the piece is filled in. I would make a hammer form. the better the fit up the less warpage. you'd be surprise what you can accomplish with hand tools and a lot of patience.
Sounds solid Going to try this I think as I have no gas torch to heat Very basic tools here lol
 

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