Homemade XS1 XS1B XS2 TX650 gas cap seal

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Edit: this project ended in failure, see the results at the bottom of the page.

The other day, I took my XS2 out for its first shakedown ride after rebuilding the top end, and also my first ride with my freshly painted gas tank. My first stop was to fill up the gas tank, after riding for a while I noticed a thin stream of gas trickling down the side of the tank. Oh no! This will never do! :yikes: Fortunately the paint proved quite tough, I wiped it off and when I got home I washed and waxed the tank, and all is well.

Which brings me to the point of this article,

This was the culprit, the stock gasket was cracked,
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I had a replacement from Mikes XS on hand, but it is noticeably smaller, 5mm to be exact. It’s just too small, when I closed the cap, instead of sealing, it was squeezing down inside the neck of the filler.
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They are not available from Yamaha, and I found a NOS on EBay. But I thought I’d take a crack at fabbing one up. I was looking for rubber sheets 2mm thick on EBay but mostly they come from China and I didn’t feel like waiting. So....what to do? I have some old inner tube scraps that I keep for all sorts of stuff, they are only half the thickness I need, so I’m going to cut two of them and laminate them. I traced out a pattern on the scraps.
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After cutting them out, I cleaned them with acetone and I spread a thin layer of Black RTV silicone on each piece , let them get tacky then placed the sticky sides together, laid it on my bench and placed a block of wood and a heavy weight on top and left it overnight. The results......
The new one is now the same dimensions as a NOS one
584AF68C-7E57-4434-964C-3FEAB04FD258.jpeg


With one small difference, my homemade one is .5 mm thicker
D91B9D53-6573-4939-B826-ADB81C457884.jpeg


It now reaches all the way to the edge of the cap, it closes like it should and fits much better. And it cost me nothing.
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Credit for this idea goes to @TwoManyXS1Bs , who bought the proper 2mm sheet of rubber and machined out a perfectly cut factory replica.....of course! :laugh2: I’m just a cheap hack working with scraps and scissors.
 
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Bob! Don't forget to tell the folks about your "spacing washer" trick...

What Steve is referring to is actually another of his very good ideas. These early gas caps close at a very steep angle, where the cap gasket first makes contact, about like what is shown in the upper arrow,
986CA60F-988D-4DCB-B2EF-3B91F5E7788D.jpeg


The effect then is that it puts the whole spring loaded sealing surface in a bind and makes the cap very difficult to close. By adding a small washer under the bolt head, it compresses the spring enough to let the cap drop down to a much more reasonable angle ( like the bottom arrow ) and the cap closes much easier.
14CCD988-5634-41CA-AABA-4AC5CD49CDF3.jpeg


Again, I can’t take credit for that idea, but it sure works great!
 
My homemade neoprene seal still looks like new...

I was planning on updating this thread soon. Might as well do it now. I was trying to remember what kind of rubber sheeting you ordered. So neoprene huh?


Bob, let us know if that innertube rubber holds up against gasoline. I've tried using it as a temp gasket in the past and it seemed to break down and swell.

It is indeed swelling, the inner tube material does not appear to be suitable for this application. I bit the bullet and ordered the NOS gasket that I showed above.
 
I never did post any photos of what this homemade gasket looked like after being on my tank for a while, it’s not pretty. My two pieces of inner tube , swelled, curled and delaminated from each other.
Here’s how it looked mounted in the gas cap,
74B469F1-DB6D-4015-A8E4-275A7EBBBD0F.jpeg
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And next to the NOS factory replacement.
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And the new gasket, being installed.
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I recently replaced my gas cap seal with one from XS650DIRECT. After I installed it the right side up, it fit nice and snug and seemed to be sealing well. A week later I popped the cap open and the seal looked like a Kardashian’s lips after a Botox injection. Any other sources for decent quality gas cap seals?
 
I recently replaced my gas cap seal with one from XS650DIRECT. After I installed it the right side up, it fit nice and snug and seemed to be sealing well. A week later I popped the cap open and the seal looked like a Kardashian’s lips after a Botox injection. Any other sources for decent quality gas cap seals?

Wow! Before I built that homemade gasket, I had a replacement gasket from Mikes, but the dimensions were wrong, too small diameter to seal, but it was not affected by gas. It didn’t swell. 2M wrote about buying a sheet of 2mm thick neoprene rubber from EBay and cutting his own. I was going to do that but I found a NOS gasket on eBay that was cheaper. You might look for a NOS yourself.
 
Spend the money on an OEM seal. My 650 still has the original and the bike was manufactured late 1982.
I think Sumo Rubber has them too. Someone needs to try them and report to the group.

I don’t believe you can buy them from Yamaha anymore can you?
 
Was the gas cap seal available as an OEM replacement part for a ‘76? Can’t find a part number, was going to search ebay
 
Was the gas cap seal available as an OEM replacement part for a ‘76? Can’t find a part number, was going to search ebay
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This is snipped from the XS650C fiche.

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This is the XS650SK. AFAIK, the cap is the same. The gasket is shown only on select model years.

2M0-24641-00-00 is the part number. $19.85 at Part Shark.
 
I made mine out 2.5mm silicone sheet about 8 years ago, it hasn't leaked yet (that I know of) I got it for free from Hanna Rubber here in KC, Used to buy a lot of stuff from them for work, I would occasionally ask if I could dig through their drops. They always obliged, and rarely ever charged me more than $1-2 if anything.
 
Some folks use a radiator cap seal on the later fuel caps. When OE is available, I almost always go that way. It usually proves to be less headache to fix it once and be done.
 
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