Topic: Leaky Petcock

[rddcw]

Sorting out the fuel petcock issues on my 74’ CB 750 K. Prior owner used silicon on the mating surface of the tank and petcock. Instead of replacing the rubber gasket , he just band aided it. So after flushing out tank decided to replace the stock petcock assembly. After installing new one, just a cheap Chinese knock off, leaking at Stop position. Stop removed the diaphragm and O ring from the new one and used on the original. Still drips on the Stop position but much slower. Any ideas to correct this issue 🤷‍♂️

[BenelliSEI]

Clean the face of the selector and polish it smooth. Replace the rubber.

[bryanj]

Have you got the proper thick fiber washers under the heads of the screws holding petcock to tank? If not gas will always leak through to outlet spigots

[rddcw]

Fiber washers and screws are new but that might be a possibility. I can compare with the original fiber washers or even double up on them 🤔
When you say polish the face of the selector. You mean the side of the valve lever that faces the diaphragm ?
And am using the new diaphragm from the repo fuel cock. It appears to be good but I can compare it with the old one ad well.

[rddcw]

So far so good 👍. Compared thickness of new fiber washers with old. Seemed to be about the same but decided to double up on them when securing petcock to tank. Polished the selector as suggested and even reused the old rubber diaphragm as it appeared to line up better inside the petcock. Still very pliable. Anyway buttoned it all up and tested it with fuel in the tank. No drips in the stop position and it’s been a few hours inspecting it intermittently. So hoping I got it 🤞
Appreciate All the Help Again 😊

[HondaMan]

Where did you get that petcock? I might buy one to see if I can make them better, too. I've got 3 CB750 tanks that need one!

[rddcw]

VintageCB750. I believe they are out of Canada

[rddcw]

I emailed him about the petcock issues. If he’s unable to credit me back as I robbed the O-ring that seals it to the tank as mine was pretty non existent, I could mail it to you. Wasn’t that expensive. Didn’t come with mounting screws so I purchased a couple from him but used the fiber washers.

[bryanj]

The proper Honda part fibre wahers are both very thick and VERY expensive for what they are, i have had about 70% sucess using the rubber insert "Dowty" 6mm hydraulic sealing washers, seems to depend on the petcock casting quality