Need a Petcock ASAP!!!!

Wanting to start my Norton which been doing a mild restoration the last few weeks. So last thing was putting the petcocks on tank soon as put gas in the tank they started leaking. I order them from Norton Parts place which will take a week to exchange, but I want to start it now. Does anyone know of a general petcock that would fit or know if the 1/2 fine threat is standard in a bike shop??

Where are ya? Maybe I could hook you up.

wrap the petcock threads with some plumbers tape and reinstall, that should stop the leaking

at least enough to go for a ride!

Problem with the petcocks is the cheap ones use a rubber seal around the valve, like a short piece of hose with a hole straight through the side. Once they've tasted ethanol in fuel, they swell and either cut fuel flow to a dribble or leak, or both. The expensive ones use a brass tapered valve similar to the original plastic one with a sealing O-ring under the spring, washer, and retaining ring. Though better than the cheap ones, this O-ring is still susceptible to ethanol.

If your fuel valve is leaking at the threads, teflon tape should seal. If your valve is leaking out the side and you have the expensive one, you can pull it apart and replace the O-ring. Grease the O-ring with dielectric grease before re-assembly. If you've got the cheap one, you're screwed.

If you have an original plastic valve, it can be cleaned and likely will seal, but this 40-year-old plastic is very brittle, and you've got an excellent chance of breaking it.

I bought the cheap ones for my Commando 4 years ago - they lasted a month. I cleaned up the original plastic ones, and they worked. I just broke the lever off my main a couple weeks ago and replaced it with the expensive one.

I just bought them, so can't take them apart, and leaking from the side. Wasn't sure if there's any could just pick up at local bike shop under another make/model that fits the 1/2 hole.

The petcock threads in the tank are close to 1/2"-20 but I don't know of any petcocks made for that and it is not correct. They are known as 1/4 Gas fittings. (19 turns per inch not 20.) It is a parallel thread not tapered. A 1/4 pipe NPT fitting is tapered and is not the right thread either. An old Harley sportster peanut tank and a lot of aftermarket tanks use the 1/4 Gas thread.

HeavyARMs said:

I just bought them, so can't take them apart, and leaking from the side. Wasn't sure if there's any could just pick up at local bike shop under another make/model that fits the 1/2 hole.

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If it is an old one, he cork has seen better days :!:
Should be able to replace this by removing a circlip.

HeavyARMs said:

I just bought them, so can't take them apart, and leaking from the side. Wasn't sure if there's any could just pick up at local bike shop under another make/model that fits the 1/2 hole.

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That hole is British Pipe Thread, so you're not gonna get it at the local dealer.

If its the $18 valve, you can't fix it because that rubber sleeve is leaking. If its the $40 valve, it should be any easy fix because its usually the O-ring. If you have the cheap ones and they're leaking, exchange them for the expensive ones.

Do you still have the old ones? If you do, take them apart, clean them up, and they should work, unless they're the cheap ones.

Here's a pic to show:


The original style is on the left. the cheap one is on the right. Instead of a tapered valve, the cheap ones use a straight shaft surrounded by a keyed rubber sleeve with a hole for fuel. This rubber is not ethanol-safe, and will last a very short time before it stops working (leaks or swells to block the passage, or both)

The expensive ones look like the original, except the taper is made of brass instead of plastic and won't seal fuel-tight in the body. The wide end of the taper, just under the washer and spring, has a groove and an O-ring to seal it. These things will last indefinitely, because the o-ring can be replaced, but if you use ethanol fuel, you need to replace the O-ring with neoprene or viton.

My originals had brass tapered valves, and they work if lapped into the body and replace the o-rings. Trouble is there is no adjuster nut on them and no space to put one on it so you have to use them in what ever position they tighten up.

I got some BAP ones ($30 at OB) and they work so far. I got some from Clubman that have the supposed 'ethanol resistant' rubber in them, but who's to say, I haven't put them on yet. But they do look original, except for the shiny chrome and they have a lock nut.

You might have to tuff it out until you get new ones. If you want to spend $$$ there are plenty out there to select.

Dave
69S

Get a set of BAP petcocks and never look back. They are the only petcocks I have found that actually work and they are not expensive. I generally try to run ethanol-free fuel but can't always find it. I have several sets of BAP taps that are running leak-free for 7 years now

I think the OP was asking if they are Norton specific, or could a petcock from some other bike work? If there is a brtibike shop near you, the petcock is the same as a vintage Triumph/BSA if that helps.

concours said:

I think the OP was asking if they are Norton specific, or could a petcock from some other bike work? If there is a brtibike shop near you, the petcock is the same as a vintage Triumph/BSA if that helps.

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As long as they are 1/4 BSP, they will fit!!

concours said:

I think the OP was asking if they are Norton specific, or could a petcock from some other bike work? If there is a brtibike shop near you, the petcock is the same as a vintage Triumph/BSA if that helps.

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Actually BSA used a different size on some models so you need to be sure that it is 1/4 BSP (British Pipe Thread). Parallel thread, not taper as a previous poster has mentioned.

I've had nothing but trouble with all the above mentioned petcocks. The BAP ones I bought from a reputale Norton parts place were made of junk pot metal & one broke leaving the threaded part in my tank & no I didn't crank super hard on it. I finaly got some of the billet alloy kind as sold by British Parts Supply. Do a search & read up on them all.

gtsun said:

I've had nothing but trouble with all the above mentioned petcocks. The BAP ones I bought from a reputale Norton parts place were made of junk pot metal & one broke leaving the threaded part in my tank & no I didn't crank super hard on it. I finaly got some of the billet alloy kind as sold by British Parts Supply. Do a search & read up on them all.

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Weird. I have 4 sets of BAPs running now for several years and have used them on another couple of bikes I have sold and all have been perfect. You must have run into a bad batch. I do like the look of the billet ones you mention a lot but they are spendy!!