Petcock issues - "On" will empty tank, no reserve

[cecil_t]

My '80 XS400 has a vacuum operated petcock. It was leaking, and I ordered a rebuild kit, and it was still leaking. After finding a detailed thread here on this forum I re-rebuilt it and now the vacuum operation seems to be working OK. I have a manual on/off valve installed in the fuel line under the petcock just in case.

However, I have no reserve. The "on" position on the petcock will drain the tank completely. I thought there was possibly an internal leak in the petcock that was leaking from PRI or RES to the On position but since everything else seems to be working I don't think that theory is holding water anymore. I have a scope I put into the fuel tank and I see a small oval shaped tower sticking up a few inches from the petcock, where I assume both pickups are inside (is that a screen filter?).

So my question is this - what could be wrong?

 

[Scorpio1963]

Its possible that when you put it together the plastic piece has channels in it and it got put on in the wrong direction.Maybe take apart again and check that.

 

[Lou Ranger]

If you didn't spin it around when you rebuilt the petcock, then likely a PO did so - or, in the course of rebuilding the double tower filter did not seal.
Did you have a reserve before you did the repair?

 

[cecil_t]

No, I'm not 100% sure if it ever worked or not. I haven't had the bike that long and I just wanted to see how far a tank could go and then I ran out of gas. So that, and then some subsequent testing, is how I know there is no reserve. I'm not sure how it was before I rebuilt the petcock.

But both times I rebuilt it I put that little channel in the plastic spacer facing the outside/left side of the bike, to the rear, and slightly downward (as per the detailed article in the forums here). I found another forum that said it should face upward (rotated 90 degrees) but I figured you guys know what you're talking about more than those other guys

Could there be a leak in the pickup itself in the tank? Or could the tube inside that screen filter be missing? I haven't actually pulled the petcock off the tank, I just took it apart in place while mounted to the tank.

 

[Maxim-umm]

I would pull it from the tank and check the screen/filter inside. Also, at this point it wouldn't really hurt to try out what the other forum said about positioning the plastic piece.

 

[Lou Ranger]

... I haven't actually pulled the petcock off the tank, I just took it apart in place while mounted to the tank

Well, at least you can blame the PO and not yourself at this point.
It is much more satisfying to correct a PO's mistake than one's own

 

[arfstrom]

That tower is the vacuum seal. The rebuild kit should have that, 3 or 4 other things. Pull it off the tank, it will make easier to work on.

If you found the thread, I posted pics I think I did. Of putting a' smaller print under the bigger oring. They might be still in my photo albulm, waiting for me to make a petcock thread with my doubled up o-ring trick. Willem last post a tech thread finder, within the last week, look up the phe petcock in Google, with the name on the side of the petcock. Idr. Good luck

 

[cecil_t]

OK I pulled it out of the tank and saw the tower & screen filter. I pulled it all apart and put it back together as best I could. It seemed to work properly with my tests for about 5 minutes and then starting seeping again - both flowing fuel with no vacuum and flowing fuel while in "On" when the level is too low. The seals internally must not all be properly seated, I think I'm about to give up on this vacuum valve and move to a manual one.

 

[arfstrom]

http://www.xs400.com/forum/showthread.php?t=8033&page=2
Look at these resources. Go to page one, one of my links goes to a another forum, who has some more steller pics for doing the same job. That other bike uses our same petcock. The test of the petcock is to pull of the fuel line off the petcock, then if your willing, you need to create a vacuum on the vacuum line, So weather you suck on it, or someone more willing, it should dump fuel hard and fast if its working. I did leave leave a gallon or so in the bottom of the tank, so I could test, and just left the tank on its side, while working on the petcock.

Use search terms like petcock pdf xs400, if yours is handy, then name on the side of the petcock.