Petrol tank caps

[mdt-son]

Thanks a lot, J_B !
I don't recognize dimples in filler necks of your petrol tanks. Does the filler cap really remain sealed with this kind of lock, based on friction I guess?
When visiting your shed again, would you do me the favour of measuring internal diameter of the filler neck? If it's approx. 58 mm as on mine, tank cap 033001 should fit mine.
Was ENOTS (Benton And Stone Ltd.) a supplier to AMC at the time?

- Knut

[mdt-son]

The expanding type caps never feel like they are pulling down that much... But they don't leak (I don't brim them full) and they have never come undone.

I am not surprised. There is no effective restraint vertically. The bayonet type of cap shown above should provide a greater clamping force.

- Knut

[clive]

I have this type of cap on a original ally competition tank. Provided I fill with a bit of space left it does not leak. Mind you the same applies to all the tanks I have with bayonet fittings too. I think you may be over thinking this Knut.

[mdt-son]

Clive, you may be right!

[Joker_Bones]

Yes... The two original comp tanks are just a tad over 58mm dia. The other original tank is nearer 59mm dia.
The two Indian tanks with the bayonet fit are 55mm dia.

I know what you are thinking... I always push down on the front of the cap when tightening but I don't think it makes any difference because your thumb is in the way before it's tight

Although they don't visibly leak fuel.... A mistake I made was to leave the paint on the top of the filler neck where the seal sits... petrol has gotten under it and caused the paint lift further down the outside of filler neck.

I don't know... Enots is a name I have seen on old petrol caps and taps, I've always assumed it's an old British make.

[mdt-son]

J_B, thank you so much for valuable input!
Inside and top of the tank neck will be stripped for paint. Tank cap 033001 is on my list of parts from AMOC Spares. I will report back how it fits.

- Knut

[mdt-son]

Gents, a message from Dean Nissen over at the eGroup was enlightening.
----
Scrambler tanks were redesigned for the 1965 model year. The badge hump was added and Norton, AJS & Matchless went to plastic badges with standardized screw holes so all three badges would fit any tank. The filler cap went to the aluminum 1/4 turn cap. Before that, scrambler tanks had transfers w/ no hump like the 1964 Atlas scrambler below. The filler cap was chrome plated w/ a multi turn knob that actuated 3 expanding fingers that grabbed the hole and pulled the cap down. .... The aluminum cap seals better and was probably cheaper to make. Dean HYCAM America "
-----

So, now we know the 1965 onward petrol tanks should have two dowels in the filler neck as shown in the pictures above for repro tanks, and a filler cap featuring a bayonet type of cap providing sealing at 1/4 turn of the wing nut. There must have been at least two versions of the late type cap, the last one having p/n 033001. Attached are pictures of this cap.

I've also realized my tank is an incorrectly made repro. Bugger! Looking for a weld-in filler neck of the appropriate type.

- Knut

033001_1 fuel tank cap.png

033001_2 fuel tank cap.png

033001_3 fuel tank neck.jpg