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Always wanted to know how fuel cap works...
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Mags 1
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November 29, 2018 - 9:49 pm
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It isn't the usual Bantam type cap for a start, just a flat plain top, main problem was amount of dirt and cap wouldn't go on as far as a properly marked up Bantam one, but sometimes you have to use what you have, all Bantam stuff is now rocketing in price.

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Havn't even thought about stripping one down before, but here goes, nothing lost nothing gained, so far. People are selling new fuel tank cork sealing rings, I wonder do they advise about how to fit them without breaking them?

I started by squeezing together and flat, what looked like a common or garden split pin, but it appeared to be made of brass, not so common then.

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Simple, once concave (brass also) washer came off, outer brass cone shaped piece followed.

 

I knew there was a spring of some sort underneath the second piece of brass, but just how would you get the brass diaphragm type piece out? Even a knife blade wouldn't get between the main cap and the diaphragm type piece.

Four now on the road and at least several in bits.

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Mags 1
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November 29, 2018 - 10:03 pm
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If you have use of an air compressor of a decent poundage, you'll be in luck for next step, all you have to do is put nozzle onto small hole on cap top and pull trigger, force of air rushing through should dislodge the diaphragm, well it did for me. Just keep you hand, gloved if you wish, over the diaphragm, just in case you 'give it too much' and manage to blow diaphragm and spring down the road...

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Before trying the compressed air, I almost began to wonder if the two 'crimped in' places in brass cap were put in after rest was assembled, but I think not. Brass of diaphragm is quite thin and will bend and straighten out again many times, in my opinion.

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There's not a great lot to them, but they work well and don't often give trouble, there are three holes in all, one each in main cap, coned piece and diaphragm, there has to be of course, to allow air in to displace the fuel going out and to allow for expansion in hot weather etc.

I gave everything a good clean up, before I simply put it all back together again. Using the electric wire wheel disclosed certain numbers and letters on the coned part, not sure what they mean.

Four now on the road and at least several in bits.

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Mags 1
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November 29, 2018 - 10:11 pm
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Legend on the cone part of brass.

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Bare cap, lots of dirt around ventilation hole.

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To get the diaphragm back in, I simply bent it downwards, in the two opposing places where it would pass the locking indents, I used a three inch length of hardwood from a parquet floor which was about an inch by about a quarter inch on the end, I chiselled it up a bit to fit the space between the cone and the outer of the main cap, just placed it in the gap and gently tapped away, brass just naturally flattened back out as I went.

Four now on the road and at least several in bits.

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Mags 1
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November 29, 2018 - 10:17 pm
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The hardest thing was to open the brass split pin back out, which started with a very small flat bladed screwdriver and ended up with a thick pop rivet's sharp end, both being tapped in gently. Actually had to do this job twice, as I'd forgotten about the concave washer first time!

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Yes, it's just a split pin.

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First unsuccessful attempt.

Four now on the road and at least several in bits.

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Mags 1
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December 4, 2018 - 4:53 pm
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It appears that I've made a mistake with this cap, which didn't turn the full 90 degrees either before or after the clean up.

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This is the working side of another one that does fit one of my Bantam tanks correctly, note that the cork sealing ring is on the outside of both the coned and diaphragm type brass fittings here.

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I took the first cap in question here to bits again and removed the cork washer, this wasn't right either, as it left an eighth inch air gap between those two items, proving at least it was assembled correctly.

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I tried the bare cork washer onto the tank top orifice and it did fit, but I cannot see any of the dished in surface of washer when fitted to cap, so I can only conclude that I've run a post here with an item that doesn't really fit a Bantam tank at all.

I'm sorry for any inconvenience caused to anyone who tried to follow my example and was confused by what I posted in error, it now appears.

Four now on the road and at least several in bits.

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