Commando petcock valve - head scratcher (2015)

Today I took the Combat Commando out for a spin in the Texas Hill Country. As always, following my normal starting procedure:
(1. break clutch free.. 2. tickle each carb about 6 seconds 3. two kicks with key off to "prime" the intake, 4. One kick to start), she cranked right over on first kick, after sitting for 2 weeks.

I rode a short distance, had to stop at a shop, and as I was pulling in, the engine sputtered, wouldn't take any further throttle, and died.

I have clear gas lines, and they looked empty.. hmm, I thought, must be low on gas, so I turned on the reserve petcock (left side), saw gas flowing, tickled again, cranked on first kick again, and proceeded on my way. I stopped at a gas station, but was surprised to find I had nearly a full tank of gas.

Back home, I noted an anomaly between the left and right petcocks. The left valve ONLY moves within a 90 degree arc, from horizontal to vertical, but the right valve doesn't seem to have any constraints.. it will move a full 180 degrees, or even more, only stopped when hitting the underside of the tank.

I am just wondering if maybe something is slipping inside this petcock, so that when it appears to be in the open position, it actually isn't?

I've never taken one of these apart, so I have no idea if the construction could allow this.

Both valves appear to be original, or original style.

Should I just replace the valve with a new one? If so, best recommendation for an original-style valve?

Phil - Austin
'72 Commando Combat

Original petcock valves are cheaply made items and are widely known for leaking . Why screw around with stuff that is suggesting failure? Remove both of them and replace them with BAP valves. Watch out for counterfeits. Or....if you insist on OEM appearances, check
out Andover Norton's selection of valves, or other favorite vendors. The last thing you want is a tank full of gas bleeding into your
crankcase.

1+ on BAP or other high end taps if the treads match up. Mainly posting that I found out the hard way if original and maybe after market taps are stored after use, dry, like time to re finish tank, their seals dry up distort and surfaces etch-corrode so do not stay functional long if restored so I now keep em in no ethanol gas/diesel mix in a sealed jar. A slow tap leak can pass thru carb to wet sump.

Hi
The rubber insert in the petcock, can revolve in the housing, also if it has it can also slice a piece of the rubber off, then blocking the valve. My next step would be to replace the valve.
Peter

Also the petcock lever can rotate on it's fixing pin and the lever will then rotate beyond the 90 degree stops on the petcock body or in the opposite direction.

The market is flooded with petcocks that have cylindrical rubber sleeves that are badly affected by petrol and ethanol. The rubber can swell to a point it almost closes the hole up. They can also rotate, fully closing the hole off.
Matt at CNW sell nice but non std looking taps with reserve function. If you want original ish looking taps, I have often used taps supplied by Andy Molnar for Manx Norton's, which have a ground tapered brass on brass seal and very good flow. Only down side is their is no reserve function.

In America we have E-10 and can rarely find real gasoline. What does Austin Texas use?
I have bought sealed Andover Norton petcocks and had the rubber liners swell up from ethynol in about 60 days after installation.
Swell up means to restrict down to a large pin hole by the rubber bush...it did NOT rotate or it would be 100% closed.
Granted what does AN mean....South Hampton/BSA Regal on those bags not Hungerford.
Knowledgable people in the parts industry say that has been fixed but who knows what old stock is still left in the supply pipe line.

Matt at CNW sell nice but non std looking taps with reserve function.

+1
Been running mine for about 9 months w/ 10% ethanol still turn smoothly and no sign of gasket swelling. Can't go wrong with anything from Matt.

Pete

The stock BAP Taps are still one of the cheapest and best options

and can be easily sourced from both Norton and Triumph shops

Phil,

Forgot to mention this. Use Dowty washers and some Permatex thread sealer on installation. Combined they will prevent leaks without over tightening.

Pete

The petcock is normally open at 90 degree turn. If one of your's is moving to 180 degrees, likely it's closing again.

showing my ignorance here. what is a BAP valve, any pics or info please

It's just another petcock available from nearly anyone, OB, Clubman, take your pick. As I remember they were about $30 for the pair. They don't look like the EW taps though. I have them on mine.

BAP's




CNW

Hi pauldridge.
Re your: "...best recommendation for an original-style valve?"
In good faith, I cannot.
I use SMC ball valves flush with base of tank then to linked carbies.
RH side on for main and LH side on for reserve.
When the tank is empty only fumes are left.
Ta.

needing said:

RH side on for main and LH side on for reserve.
When the tank is empty only fumes are left.
Ta.

Click to expand...

You have this backwards - Right is Reserve

p12 in the Riders Manual - http://britmoto.com/manuals/Manuals/Riders_2.pdf

Right on for main will (un)surprisingly get you on fumes!

gortnipper said:

needing said:

RH side on for main and LH side on for reserve.
When the tank is empty only fumes are left.
Ta.

Click to expand...

You have this backwards - Right is Reserve

p12 in the Riders Manual - http://britmoto.com/manuals/Manuals/Riders_2.pdf

Right on for main will (un)surprisingly get you on fumes!

Click to expand...

That's how I have mine setup but the only reason I know is that is the way it was when I bought it in '74. Is there a difference in the tank that I don't know about? Main or reserve is based on the height of the tap in the tank, correct?

gortnipper said:

needing said:

RH side on for main and LH side on for reserve.
When the tank is empty only fumes are left.
Ta.

Click to expand...

You have this backwards - Right is Reserve

p12 in the Riders Manual - http://britmoto.com/manuals/Manuals/Riders_2.pdf

Right on for main will (un)surprisingly get you on fumes!

Click to expand...

Taps were swapped over on late models:

http://britmoto.com/manuals/Manuals/Riders_4.pdf

However: the main and reserve taps can of course be fitted whichever side the the rider prefers.
reserve-petcock-preference-port-stern-t20807.html

gortnipper said:

needing said:

RH side on for main and LH side on for reserve.
When the tank is empty only fumes are left.
Ta.

Click to expand...

You have this backwards - Right is Reserve

p12 in the Riders Manual - http://britmoto.com/manuals/Manuals/Riders_2.pdf

Right on for main will (un)surprisingly get you on fumes!

Click to expand...

Nope. With my tank, I switch on RH tap and ride until the top and RH flank is empty (bike coughs).
I leave my RH on the throttle and reach down with my LH to switch on reserve LH tap (for the LH flank of the tank).
IF I ride until the LH flank is empty (bike coughs then stops) and I only have fumes left.
I try very hard to avoid this last scenario as it makes me sad.
Ta.

L.A.B. said:

Taps were swapped over on late models:

http://britmoto.com/manuals/Manuals/Riders_4.pdf

However: the main and reserve taps can of course be fitted whichever side the the rider prefers.
reserve-petcock-preference-port-stern-t20807.html

Click to expand...

Yes, but the OP has a '72 and I was pointing out the stock setup.

needing said:

Nope. With my tank, I switch on RH tap and ride until the top and RH flank is empty (bike coughs).
I leave my RH on the throttle and reach down with my LH to switch on reserve LH tap (for the LH flank of the tank).
IF I ride until the LH flank is empty (bike coughs then stops) and I only have fumes left.
I try very hard to avoid this last scenario as it makes me sad.
Ta.

Click to expand...

You have setup yours to your own delight, backwards from stock. No prob.