Early fuel caps - Any alternatives or substitutes available ?

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Grewth

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If I understand things correctly, the early type '70 to '73 caps are no longer available from Yamaha, nobody makes a pattern replica, and good (???) used ones fetch silly prices when they come up.
Apart from the cap itself, there is the mazak fitting which is attached to the filler neck too.
Apparently these break all too easily and offically cannot be replaced due to the tank neck being peened over.
So has anyone managed to fabricate their own replica filler cap, or even graft a completely different neck and cap onto an early tank ?
I'm just trying to weigh up my options here.
 
You can buy replica 70-72 caps from Mike’s. It’s the 73-75 caps that are not reproduced.
 

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willis said:
You can buy replica 70-72 caps from Mike’s. It’s the 73-75 caps that are not reproduced.
Click to expand...
Ahhh!
Thanks very much, I have been mis-informed.
Now I have the problem of the broken mounting ring that's peened onto the filler neck.
It seems to be made from Mazak which simply can't be welded.
Maybe I'll have to fabricate something from steel to replace it ?
 
There are thread here about those filler necks being of different alloy. I am not up to speed on them but it memory serves correct, eithe Dogbunny or 2many has written about them. Try a search with filler neck or something of that sort and see what comes up.
 
As I see it, you have two choices:
The first is to find a 70-72 donor tank, and remove the neck from it.

s-l1600.jpg

The neck is Mazak (or whatever) that has been cast around a steel collar. That collar is welded to a slightly larger steel collar on the tank. If you grind off the weld, the neck is freed, and can be used to replace your broken neck. I routinely free-up 73-75 necks (as the pic shows) from donor tanks all the time, it's not hard to do.
The problem is that the 70-72 donor tank is going to be more valuable with it's good neck as it already is, compared to your broken tank.

s-l1600 (1).jpg

https://www.ebay.com/itm/125000863024
Your other choice is to completely remove your broken neck, and replace it with a complete bolt-on cap assembly like this. There are many out there. Obviously you need to check dimensions and find one that is big enough to cover the hole that will be left when you remove the neck.
 
DogBunny said:
As I see it, you have two choices:
The first is to find a 70-72 donor tank, and remove the neck from it.

View attachment 213859
The neck is Mazak (or whatever) that has been cast around a steel collar. That collar is welded to a slightly larger steel collar on the tank. If you grind off the weld, the neck is freed, and can be used to replace your broken neck. I routinely free-up 73-75 necks (as the pic shows) from donor tanks all the time, it's not hard to do.
The problem is that the 70-72 donor tank is going to be more valuable with it's good neck as it already is, compared to your broken tank.

View attachment 213860
https://www.ebay.com/itm/125000863024
Your other choice is to completely remove your broken neck, and replace it with a complete bolt-on cap assembly like this. There are many out there. Obviously you need to check dimensions and find one that is big enough to cover the hole that will be left when you remove the neck.
Click to expand...
Thanks for that.
I'd rule out a modern bling filler for the bike I'm building - I want it to look as retro as possible - maybe if Mikes XS didn't have those replica gas caps at a very reasonable price, I'd be more tempted.
Looking at your sketch, it's a very similar set up to the XS650B tanks.
Quite easy to get a die grinder in there (or even a hand file) and grind away the weld, but not easy to weld a new tube in.
And as you say, these tanks are rare and expensive now, I'd hate to pay top dollar for a beat up tank, just for that ring of monkey metal, then have it break anyway.
 
gggGary said:
Iirc @Mailman used liquid steel to reattach his busted ring. Maybe he'll point you to the info if he can stop cruising long enough to do it.
Click to expand...
Exactly what I was thinking of myself.
Well basically any high strength adhesive that is absolutely fuel proof.
No heat, no distortion, no melted Mazak, no exploding fuel tank.
But with Ethanol levels rising that might not be as easy as it sounds.
 
Well personally I think that Candy Red paint job looks brilliant.
I'm having thoughts that I need to find a friend with a small lathe in his shed.
Get a basic filler neck turned from mild steel, TIG weld the ears onto it at work, then glue it into the tank with chemical metal etc.
Well that's the theory anyway.
Alternatively, I've found pressed steel filler necks which take British type 2.5" twist off caps.
On eBay UK for just £10
 

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