Topic: Fuel petcock valve question

[JS550]

Im assuming that my 750f petcock has an o-ring of some sort that goes between it and the tank? Right? And where can I get a new one? Or is there something that I can use inplace of it? Pipe tape or gasket sealer?
       Jim

[Triffecpa]

Most of them thread onto a male pipe thread bung that is welded to the tank.  If it's leaking around the threads, unscrew the petcock and wrap some teflon tape around the bung and reattach the petcock.  Others have claimed that teflon tape won't hold up to gas, but I've not had any problems using it.

Tracy

[JS550]

Ok, that's what I needed. I picked up the tank without a petcock on it, it does have the welded bung though, & seem to remember my 550 having a little rubber o-ring but I just used some gasket stuff that I'm guessing has made the petcock a permanent part of the tank! But thought I would check this time around.
                                                                      thanks

[davesprinkle]

Im assuming that my 750f petcock has an o-ring of some sort that goes between it and the tank? Right? And where can I get a new one? Or is there something that I can use inplace of it? Pipe tape or gasket sealer?
       Jim

Pipe-threads have a tapered diameter and are designed to seal on the threads.  The petcock bung is NOT a pipe-thread -- its diameter is consistent along its length.  It is designed to seal on a crush washer.  Do not attempt to use pipe tape to seal a straight thread.  It MIGHT work, but probably not, and then when it leaks, you've got a fire risk.  Just do it correctly and get a replacement washer.

[dn4911]

I took the petcock off the tank of a 550 supersport tank and it looked like there was a gasket there.  I bought some gasket material and was going to just cut out a new one.  ANy problem with that?

[davesprinkle]

I took the petcock off the tank of a 550 supersport tank and it looked like there was a gasket there.  I bought some gasket material and was going to just cut out a new one.  ANy problem with that?

Cutting out a gasket MIGHT work, depending on the gasket material and how tightly you clamp it up.  The stocker was a somewhat thick (maybe 2mm?) ring.  Sorry, I don't recall the material.  My Pingel petcock, which seals in a similar manner, includes a 2mm thick plastic sealing ring.

I would suggest ordering up the stock part.  It's probably still available and likely will cost less than $10.

[TwoTired]

What year F tank did you get?  The 77's had a different bung size.  In both cases, there is an in tank filter.  Just different styles.  The gasket is also different between them.  For certain, teflon tape is the wrong way to go.  And, if you use the white type it is attacked by hydrocarbons.  The yellow type is used for gas situations.  But, as I said, teflon tape is just the wrong application for the bung threads.  The seal is to be made against at the end of the tank bung, not the threads.

Cheers,

[dn4911]

Don't know what year the F tank is.  It came as a throw in with the 75 K1 550.  Yes the filter is inline, actually it looks from the outside just like the K filter.  For some reason I thought it was off a 76.

[TwoTired]

What is the width of the tank bung?

[jtb]

The 77&78's had a fibre washer that went inside the nut on the petcock.  They're only good for one shot.  I replaced mine with an o-ring a couple of years ago with no problems.  I got an assortment of o-rings at an auto parts store.

[ngonerogwu]

I just used a 10.8 id, 15.6 od, 2.4 section on my 77k petcock.

[uksparky]

What is the width of the tank bung?

My tank bung is 3/4 inch 1.5 mm threads....is that 16mm....or 18mm having a hard time finding petcock 90 degree