Fuel Petcock Screws

Carveacre

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I am about to start rehabilitating my rusty original 1981 XS650SH fuel tank. I have a new petcock, but it came without screws. I even have YAMAHA emblems I can paint. Can someone tell me the size and pitch so I can get stainless steel screws from Home Depot? Thanks to all. Carveacre in Alpine, CA
image.jpg
 
It takes a special screw.... not that plain wouldn't work. I think I have just plain on mine. The washer is a "fiber" washer.... for sealing.

Here's sumpin that will help for finding bolt/screw sizes. The second series of numbers in the part number is the diameter and length. In the example below, a 5mm dia screw with a length of 10mm.


1710537999058.png



So we can work out from the part number below that you need screws 6mm in dia and 8mm in length.
https://www.partzilla.com/catalog/yamaha/motorcycle/1981/xs650sh/fuel-tank


1710537949734.png
 
I'd guess they'd work just fine.
 
Don't forget to include the sealing washers for the bolts or you are going to have a leak.

I've found the ones from Yamaha work best and can be ordered directly from your local dealership.

The aftermarket sealing washers I've used have been junk and were prone to disintegrating on install.

Once everything is buttoned up, it is also worth testing how well the petcocks hold fuel with the tank off the bike (don't ask how I know 😉).
 
Don't forget to include the sealing washers for the bolts or you are going to have a leak.

I've found the ones from Yamaha work best and can be ordered directly from your local dealership.

The aftermarket sealing washers I've used have been junk and were prone to disintegrating on install.

Once everything is buttoned up, it is also worth testing how well the petcocks hold fuel with the tank off the bike (don't ask how I know 😉).
I used copper washers under each screw head, can be seen in the picture. I annealed them before use so they're nice and soft, hopefully they won't leak. I'll know very soon.
 
I agree on the copper washers, I’d be worried that they would leak as well. I’ve never had an issue with the fiber washers even re-using them a few times. I like that you have to screw them onto the screw threads. IMHO If the gas can get past the threads the chances of a leak are too great. Just my :twocents: and maybe some members have used them with no issues, I just prefer not to gamble.
 
Really? I'm all ears, why not annealed copper washers? I can change the ones I used if I need to. Thanks.

The OEM washers are a special hybrid type that as Wingedwheel mentioned, are almost and interference fit on the bolt. I don't think copper would be soft enough to provide enough sealing (even after annealing).

Last time I purchased the Yamaha ones, they were a couple bucks cdn each, but were well worth the investment.
 
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The OEM washers are a special hybrid type that as Wingedwheel mentioned, are almost and interference fit on the bolt. I don't think copper would be soft enough to provide enough sealing.

Last time I purchased the Yamaha ones, they were a couple bucks cdn each, but were well worth the investment.
Thanks, that's good to know. I'll look some up.
 
Really? I'm all ears, why not annealed copper washers? I can change the ones I used if I need to. Thanks.
like they say just not soft enough.
If the oem ever go extinct casting lead washers might be the hot tip.
heck, cast em right on the screw..........
other possibilities:
faucet washers are a hard yet deformable rubber.
remove the metal/rubber washer from a polebarn metal screw.
You might even have a couple of those in your parmesan cheese jar screw collection.
 
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lijke they say just not soft enough.
If the oem ever go extinct casting lead washers might be the hot tip.
heck, cast em right on the screw..........
other possibilities:
faucet washers are a hard yet deformable rubber.
remove the metal/rubber washer from a polebarn metal screw.
You might even have a couple of those in your parmesan cheese jar screw collection.
Thanks. I did anneal the copper before use. So I'll give it a go as it is to see. But I've looked up the Yamaha washers and they're readily available if I need some. The Yamaha application list for those washers is huge. I doubt they'll go unavailable anytime soon.
 
Consider the application, the tank is thin sheet metal you are compressing a big oval o-ring seal, you could deform things by over tightening.
PS I remove any remaining paint from the tank face before installing the petcock.
 
Consider the application, the tank is thin sheet metal you are compressing a big oval o-ring seal, you could deform things by over tightening.
PS I remove any remaining paint from the tank face before installing the petcock.
I have actually polished the tank surface under the petcocks. The tank has been cleaned and sealed internally, it's good to go. But I don't want there to be any traces of paint on the surface of the tank where the petcocks are fitted.
 
I've been using copper washers with button head screws on my XS2 for 5 years now without a leak. Also have used them on other tanks without any problems.
I would be leery of using something made for sealing water in a fuel application.
The factory paint on the tanks doesn't seem to have any problem with gas. I do coat the o-ring with high vacuum grease.
 
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