Vacuum Petcock rebuild kit - FAIL

[jetmechmarty]

I've had a couple of failed attempts at rebuilding vacuum petcocks. I thought the o'ring was wrong. I tried that. No help. Currently, I'm running some manual taps.

Greg, a Yamaha enthusiast on another forum got to the route of the problem. https://www.xs650.com/threads/81-special.65260/page-4

I have an unused diaphragm from Dime City Cycles.
https://www.dimecitycycles.com/petc...?fits-motorcycle=Yamaha/XS650/all-models/1981


I measured the pin at 18.14 mm.

I measured four OE diaphragm pins. 18.75, 19.06, 19.06, and 19.02 mm.

I believe the diaphragm pins in the kit are at fault. Be aware before you buy.

It says in the description that the pin is 18.5 mm long. That isn't long enough. I should have measured first, then read the description.
I believe the issue is K&L Supply 18-6633. That's the part every vendor sells. It's no good. No matter where you go, you get the same failure. The fuel will not shut off.

There is a fix for this.
(6) Vacuum Petcock rebuild kit - FAIL | Yamaha XS650 Forum Scroll down to post #10.

[Radioguylogs]

We had a similar conversation on the XS750/850 Triple forum before it became defunct.

Th K&L kits didn't work on the vacuum petcocks.

One member measured the rebuilt kit and found the pin was too short.

I don't remember their best solution, but it was not the same as the XS650 solution. I think the XS650 solution seems to be the better idea.

I ended up going manual. On one XS750, I modifed the OEM to be a manual petcock. On the other XS750, I changed to an aftermarket manual petcock.

[DEEBS11]

The low quality of repair parts in the last few years makes it difficult to keep things running smoothly on all fronts. Its across the board from appliances, electrical, plumbing to construction & vehicles. I don't know where this situation is headed. I tell the kids that I am the last of my kind. A man who can fix what is broken. A unicorn. We are the last of our kind and we are being fazed out.

[DEEBS11]

Now that I got that off my chest, all my bikes either came stock or have been converted to manual petcock. Can't totally trust auto diaphragms. If they fail, you have no clear indication that they have failed and you end up with fuel watering down your engine oil which can cause catastrophic damage. My Kawasaki's have been converted to Pingle units and my XS11 uses these units shown which I have no doubt are Chinese but work well as I have left the full tank on the ground for a few days at a time when doing repairs and no fuel leaked out of them. So far.

[jetmechmarty]

DEEBS11, to your point, those are not plug 'n play. I installed one last spring. I had to buy a rebuild kit. The valve face had to be ground flat. I safety wired the screens on, so they wouldn't fall off. The outlet was 3/16 instead of the 1/4 I needed, so I had to deal with that. Oh, I had to source a 90 degree outlet, also 3/16 and shim it to the correct position. All more work than fixing the OEM petcock should be.
Meanwhile, I bought a brand-new Yamaha over forty years ago. The vacuum petcock has never leaked or failed to open. I have complete confidence in it. The tank is full and off the bike as I send this. It isn't leaking.
My Eleven Special retains its vacuum shutoff valve. I'll be repairing it soon. I acquired that bike in 2003 with 10K miles on it. Obviously, it did a lot of sitting.

[jetmechmarty]

This shows the 90 degree fitting before shimming. I can't have the fuel line touching anything. Today, it doesn't touch anything and wears an OEM shroud. Also shown is my hillbilly line installation. There's a short piece of 3/16" Tygon with 1/4" tubing slid over it. Intent is still to go back to an OE vacuum tap. But, I did all this work!


That's 0.020 aircraft grade stainless safety wire as reinforcement. The screens are known to be found floating in the tank.

[DEEBS11]

Nice bike. Not sure if we purchased the same petcock as there are a few styles out there. Mine did come with optional elbow fittings which I did not need with an XS11 Standard. I did, however had to switch the outlet on the right hand petcock so the fuel output faced back towards the carbs. Other than that they were plug and play. Not original OEM but functional replacements. A decent option.

[DEEBS11]

I like what you did to retain the screens. They (the petcocks) do look the same. I better check mine to see if the screen feel off on either side.

[DEEBS11]

Here is a few more. One thing about my units are the rather high reserve pipe. One of these is a Special and one has a lower reserve pipe like yours.

[jetmechmarty]

XS650 touring with manual petcock. Honestly, my biggest issue with it is that I can't remember to turn it off when I shut down. I have forty years of auto fuel shutoff training.

It's January and frigid outside. What else do you have to do?

[DEEBS11]

I think this one is also different in it has only one output instead of two. Maybe an older version that could not be used on either side.

[DEEBS11]

And here is a down facing auto unit.

https://www.ebay.com/itm/11584119017...Bk9SR66ZlPekYw

[DEEBS11]

This is neat. An in-line auto unit.

https://www.ebay.com/itm/23502051708...Bk9SR7CZlPekYw

[jetmechmarty]

I reached out to K&L about it. Let's wait and see if they respond. I like to think they will. I will post it here if in fact I get any response.

[Mathh]

And here is a down facing auto unit.

https://www.ebay.com/itm/11584119017...Bk9SR66ZlPekYw

Described as XJ1100 Maxim tap with vacuum which is not correct...