Gas cap and petcocks for an XS750/XS850 tank?

scotts

I've been doing some research but I was wondering if anyone knew what gas caps and petcocks work on the 750/850 tanks? I'm referring to the "standard" tanks with the scalloped sides.
I "believe" that an early, standard XS650 gas cap and petcocks work, but would like to hear from anyone that has experience.

scotts

I picked up a tank off an '80 XS850 which is the SAME as the XS750 tank that everyone uses for a cafe racer. It came without petcocks or a gas cap. Actually, it has one petcock but it's busted.
I've searched, researched and then re-researched this tank. I've got the gas cap figured out (MikesXS or early XS650s). The petcocks have me cross-eyed. I even joined a Yamaha Triples forum and still got conflicting answers.
I'm told that the late model non-vacuum petcocks Mikes sells will work, BUT...I'd rather not run a non-vacuum petcock, let alone a pair of them. It's just a matter of time 'til I forget to close them, pollute the oil and seize the motor.
I measured the holes on the tank. From hole center to hole center is about 1 27/32" or 46.74mm.
One thing I've been told to be careful of is that the Special petcocks, while they fit the holes, might interfere with the seam on the bottom of the Standard tank.
I think..."THINK"....that early XS650 tanks with dual petcocks will work.
Can ANYONE help me shed some light on what petcocks (from any Yamaha model) will work on this tank?

scotts

Well, luckily, I found a pair of petcocks from an '80 XS850 and the pics of the left petcock match exactly what I have. The right petcock is from the same bike and is a mirror image.

Here's what I've been able to deduce so far....I believe that the early XS650 petcocks will work, as will some from the XS750. The bolt pattern is the same. The difference is in the direction that the vacuum barb and/or fuel outlet face. The XS750/850 standard tanks have a seam on the underside so a petcock from, say, an XS750 Special (or whatever) may bolt up, but it may or may not hit the seam, it may or may not have the outlet facing the right way (which might not matter....just route the fuel lines differently), and it may or may not have the vacuum barb in the "original" ocation.

Some "Special" petcocks will work on a "Standard", some will not because of interference issues. You may also be tol that a "Special" petcock won't work when, in reality, it will work just fine but may not be an exact match.

So, that said....if I had a bike wrecking yard near me I could probably just go try a few out and find something that would work. May not be correct, but would work. Since I don't have that luxury and all my shopping is over the internet, I have to be pretty darn sure it will work.

And the part numbers are totally confusing. Someone gave me a list of bikes/years that would interchange, but when I look at the Yamaha parts site they ALL have different part numbers. And when you see pics, they are just ever-so-slightly different. Maybe not enough to matter, but it might.....

Confusing, ain't it?!

Cafe_Shop

Here are the parts I'm running on my xs750 tank with Mike's XS part numbers:

20-0019 petcocks - non vacuum type (78-84)

20-0033 Gas Cap with Keys

scotts

Cafe, I know that Mikes gas caps work and they are within a buck or two of what's available used. Guess which one I'll be using? Wink

The non-vacuum petcocks...well, I've heard pluses and minuses. Some guys on the Yamaha Triples boards still have trouble with spoiling the oil with gas. You can say that's a faulty float deal, but they still deal with it. And I can't trust myself to turn off a petcock everytime I stop, let alone two.

funranger · 650Rider Supporter Joined: Feb 18, 2005 Posts: 18

Hello picked up A 850 tank if you have info on how to put it on the bike I would love to hear it

scotts

I haven't installed it yet, but if you do a search here for the XS750 tank it's the same. Basically, from what I'm told, you have to "reverse" the cups/rubbers at the front of the tank/frame and bend down the tab at the back.
I had a hard time finding detailed instructions/pics myself, so when I do get around to do it I'll take detailed pics and be sue to post for future reference.

Landmonster · Full Member Joined: Mar 11, 2009 Posts: 13

Anyone had any further developments on the 850 tank swap?

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Yamaha xs650