Petcocks?

[XSTrey11]

Yeah my 78 petcocks are different as well. Mine have the partitioned o ring and the different tower like steve is talking about.

Even if the kit came with the partitions you could just trim the pieces off anyways.

Ture. You think all the other parts would be acceptable then? Do these kits come with instructions at all cause I'm worried about being able to put it all back together when i get it. Although I'm sure ya'll will be helpful if I need it that bad.

[natemoen]

Ture. You think all the other parts would be acceptable then? Do these kits come with instructions at all cause I'm worried about being able to put it all back together when i get it. Although I'm sure ya'll will be helpful if I need it that bad.

Haven't had to buy a kit but I doubt they would come with instructions. The parts should all be fine though. Like Cy mentioned, and I have heard others mention before as well, you may need to stretch the spring out a little on the vacuum diaphragm a little.

[crazy steve]

After looking at your pics again, I'm sure you (and Cy) have non-stock petcocks. I double-checked the parts fiche, and it shows the same filters and o-ring for all years standards, as well as 'complete assemblies' for parts replacement. Also, your turn-on handles don't match (and neither looks quite the same as OEM), so that's another clue that they're not original. I suspect that Yamaha may have bought these from an outside supplier (like the carbs, forks/shocks and much of the electrical bits), so there may varying versions for different bikes, but they share the same internal parts. If CY had success with the XS kits, there's no reason you shouldn't either.

And don't worry about those oval base seals; a 2" OD, 1/8" thick o-ring will work just as well, and should be cheaper than the $10 a pair for the custom-fit ones; just make sure you get a viton or nitrile rubber in these...

[skids]

And don't worry about those oval base seals; a 2" OD, 1/8" thick o-ring will work just as well, and should be cheaper than the $10 a pair for the custom-fit ones; just make sure you get a viton or nitrile rubber in these...

That is true as I have done that, but you need to do something to prevent leakage down the bolt threads because they will not be isolated anymore. Fiber washers on a flange bolt will work but do not use metal washers with that method.

[crazy steve]

I never understood why they bothered with the 'partitioned' o-rings; the bolt holes aren't 'blind' so fuel can seep past the threads anyway, and they used fibre sealing washers on the mounting bolts anyway (or maybe because)...

[cywelchjr]

I looked at my spares again, and I have the partitioned o-rings on mine, I thought they didn't. Then I looked at my XS400 which has approx the same petcock, and it doesn't have the partitioned o-ring, but has the same hole size and will bolt up to the gas tank of a standard, however if you use a set of them, one will work backwards.

[jetmechmarty]

I have XS650 parts in boxes. I have both petcocks you speak of. The plastic pressed in tower model is the later one. The bases are very similar. BTW, XS650 petcocks fit the XS11 standard, so new ones are available from the usual sources. (only left side is available, but works on both sides)

Marty (in Seattle)

[XSTrey11]

I have XS650 parts in boxes. I have both petcocks you speak of. The plastic pressed in tower model is the later one. The bases are very similar. BTW, XS650 petcocks fit the XS11 standard, so new ones are available from the usual sources. (only left side is available, but works on both sides)

Marty (in Seattle)

That is phenomenal! What are these usual sources?

[jetmechmarty]

www.650central.com (my favorite)
www.mikesxs.net

You want the vacuum petcock replacement for 1978 to 1984 XS650. These are manual petcocks.

Marty (in Seattle)

[XSTrey11]

www.650central.com (my favorite)
www.mikesxs.net

You want the vacuum petcock replacement for 1978 to 1984 XS650. These are manual petcocks.

Marty (in Seattle)

I'm not quite sure I understand. I cannot use the non-vacuum type petcocks off of the xs650? Like the ones for sale complete on mikesxs.net?
http://www.mikesxs.net/products-34.html#products

[jetmechmarty]

Yes. The non-vacuum petcocks are the replacement for the vacuum petcock. The '78 to '84 XS650 uses the identical petcock to the one on the left side of the XS1100 standard. (not the Special) When mounted on the right side, the handle positions will be reversed, but it will work fine. Mike's XS Part #20-0019 is what you want.

[XSTrey11]

Okay well it'll go on the left side of my bike. Can I leave the right side petcock alone or will it need to be the same type as the left? Also is there a filter system of some kind on these? anything that would serve the same purpose as the orange plastic ones in my photos?

[jetmechmarty]

You may replace one or both petcocks. You remove the vacuum line to the valve you are replacing and cap the barb on the manifold.

No, there is no screen on the replacement petcock. You need to add an inline filter. I use the VISU-FILTER.

This filter is available from 650 Central, it's on the same page as the petcock. There is also a picture of where to install it. You should install two of them.

Google VISU FILTER, and you might find it locally.

[bikerphil]

On my Standard, I run just the left petcock with a blocking plate in place of the right. I can still get 160+ miles from a tank of gas. Just another option.

[XSTrey11]

On my Standard, I run just the left petcock with a blocking plate in place of the right. I can still get 160+ miles from a tank of gas. Just another option.

you don't need both petcocks? how does fuel get to numbers 3 & 4?