Pure white deposits in petcock

Ok this is a new one on me. I have my petcock not shutting off completely so I took it apart to see what's up. I found all kinds of this white, I mean pure white, deposits all over inside. Looks like calcium, from hard water, but it's not that hard. Scraped a bunch off and decided to really clean it I have soak in something. White vinegar is what I'm using now but it doesn't seem to be getting it. Anyone ever seen that before? It has to be something a PO used to maybe try to derust the tank. It actually comes off pretty easily but I have no way to get to the internal passages. Maybe I'll try a .22 caliber cleaning brush where it will fit. Carb cleaner will soften pretty quickly but won't clean it out.

Not sure what exactly you're seeing without seeing it myself, but it sounds just like the normal deposits left by gasoline.

Spray the part in WD-40 and this stuff will wipe right off. You don't have to clean every part of the petcock, just where the rubber parts contact the metal parts...

While you're at it, take your gas cap apart and clean it the same way. Those deposits accumulate in the vent passages.

I've seen plenty of gas deposits but never seen any that were this white. FYI the vinegar is cleaning it up nicely after a couple of hours of soaking. The biggest concern I had was with the vacuum valve not sealing well and allowing fuel to flow even with the engine not running. It was very hard to get disassembled because of the deposits but I was careful and didn't tear the thin rubber bellows.

I didn't describe it very well other than the color. Actually it is not real hard like calcium but more like chalk. Like I said this is a new one on me.

jdvorchak wrote: I didn't describe it very well other than the color. Actually it is not real hard like calcium but more like chalk. Like I said this is a new one on me.

Yeah. Chalky white deposits are exactly what gasoline leaves behind when it evaporates. WD-40 removes it instantly. No need to soak.

I believe that is oxidation deposits from the zinc metal in the petcock. Your guess about someone soaking the tank in acid of some sort is a good one. The petcock may be junk now. Hard to say without seeing it. If there is any pitting in the wrong places it's junk for sure. If you have a media blaster some low pressure glass bead blasting may be in order.

Turns out the vinegar soak worked great. I ended up polishing the port where the vacuum valve goes with aluminum foil, put in a new O-ring and it works perfectly now. I used WD-40 on the fuel cap to clean up the vent port and it looks clean now. I don't know how I'd bench test the vent so I went for a 10 mile ride and it was still flowing gas so I don't think I have a vent problem. Keeping the spare key in the fuel cap when I ride just in case.

jdvorchak wrote: Turns out the vinegar soak worked great. I ended up polishing the port where the vacuum valve goes with aluminum foil, put in a new O-ring and it works perfectly now. I used WD-40 on the fuel cap to clean up the vent port and it looks clean now. I don't know how I'd bench test the vent so I went for a 10 mile ride and it was still flowing gas so I don't think I have a vent problem. Keeping the spare key in the fuel cap when I ride just in case.

You can test the vent by pumping air into the tank through the petcock outlet with a bicycle hand pump. You should hear bubbles through the gas and then a hissing/humming from the cap. Pressure should dissipate completely within a few minutes.

Is your local gasoline cut with 10% ethenol? Like New York state. This methenol we run in the AA/Gasser. Has to be cleaned out while sitting if it sits longer than a week.
It will turn into a sand like substance. Marvels Mystery oil helps, along with a PTFE blower lube. I f it sits longer than 1 week.
Maybe it is a sealer in the tank?
Clean it out and start over with an inline filter.

I already put a new fuel filter on it. One that is clear so I can see what it collects.

An aside note. I changed the fuel filter in my 2010 Ultra Classic, yesterday, and found those same white deposits on the fuel pump electrical connector! I rarely if ever run any gas additive in my Harley because I ride it daily. But I'm going to put some MMO in there now. On all of my older bikes I alternate MMO and Lucas injector cleaner about every 3rd tank full because I don't ride them all daily. But I do ride them enough to run a tank full every couple of weeks. Now I'm wondering about my Honda Civic because I only drive it about once a month. .... Hmmmm
Thanks for the tip.