T140V Fuel Petcocks - and the goofy "reserve" selection . . .

[Lordmac]

The situation: Triumph fuel tanks are built so there are fundamentally two halves separated by a tunnel which mounts to the large frame tube.
Imagine if you will, the two fuel petcocks that come stock (see photo below so you don't have to imagine) on most US import T140V Bonnevilles. Visualize that the one marked "reserve" is on the left side of the tank and the main (with that little extension tube rising up) is on the right side. Now imagine that you just ran out of fuel (on the main, or right side), and now you switch to the left "reserve" side and fuel then flows to the carbs. Okay, what about that fuel that remains in the right side of the tank which cannot flow out because the extension tube limits it? There is no balance tube under the tank which connects the right side to the left so that fuel can be used as reserve. The fuel now trapped in the right side only can be used if you get off the bike and tilt it over so the fuel can drain across to the left.

The question: How come they make petcocks that do that? I mean, is that dumb, 'er what? If there were a balance tube under the tank which connects the two sides, then the extension tube on the main petcock would make sense. But without such balance tube, in my opinion, both petcocks should drain all the fuel on their respective sides. Does anybody have a tank different than the one I have?

 

[Rudie]

Replace the taps in your photo with the Paioli type fitted to the Triumph tanks made in Italy in the 1980s, both taps have main and reserve.

Original Paiolis (60-7508 and 60-7509) fitted to tanks with 1/4"BSP threads each required a 'male-male adaptor' (83-7970) as the tank threads are female and so are the tap threads - an adaptor has a 1/4"BSP male thread on one end, M16 x 1.0 thread on the other end. Each tap-adaptor combination also requires a 00-0075 sealing washer between tap and adaptor.

Or there are 'Paioli-type' left- and right-hand taps with 1/4"BSP male threads.

Or, 83-7970 and 00-0075 obtained, much cheaper (certainly in the UK) are Italian BAP taps sold for the large capacity air cooled Moto Guzzi twins.

Btw, if the taps in your photo are also on your bike, they are not the originals. The ones in the photo are based on ones NVT obtained originally for the T160 from late 1974 then subsequently fitted to all 76 on twins until replaced by the Paiolis. The main difference between the ones in the photo and the NVT ones is the plate on the reserve tap was above and to the left of the lever - taps mounted on the tank, both levers pointed in the same horizontal direction in the off position.

Not sure why the pattern makers did not simply make the reserve tap the same as the original?

 

[Lordmac]

Btw, if the taps in your photo are also on your bike, they are not the originals.

Hey Rudie:
Yeah, the taps in the photo are ALMOST exactly like the originals on my bike. I shall explain;
The original petcocks (which I still have) equipped on my 1978 T140V (that I bought new in May of 1978) have . . . nylon shaft/valves which eventually broke on each one causing replacement with the ones shown in the picture that have brass shafts/valves and reverse-direction flags, but otherwise are pretty-much the same. I always thought, as I was tilting my bike over to get the fuel from the right side to the left, that there was something very strange about that situation. I will take a look at the taps you have mentioned and perhaps install a set of those. In the mean time, before I installed the replacement taps, I removed the extension tube from the 'main' tap so I could at least use the fuel from the right side. But, problematically, there is very little reserve capacity from the left side alone.

 

[Lordmac]

I will take a look at the taps you have mentioned and perhaps install a set of those.

I am replying to myself here, so . . .
I found a set of the taps and the adapters that Rudie mentioned (see photos below just for clarification) and thought these just might do, and for only about a hunnert bux! The only problem with these is . . . they aren't o-ree-jenny! And, my Bonnie might reject them . . .

 

[Rudie]

I shall explain

No need, I owned my T160 from brand new; as I posted earlier, NVT first sourced the original taps for the T160.

I found a set of the taps and the adapters that Rudie mentioned
only problem with these is . . . they aren't o-ree-jenny

The pattern brass shafts/valves will fit in the bodies of your bike's original taps. The reserve tap plates require a small section removing from the circular part of each plate, so the pattern plate can be removed and the original plate fitted to the brass shaft/valve; the missing section of the plate is hidden by the circlip positioned judiciously.

my Bonnie might reject them

Adapters and BAP taps not rejected by my T160 for several decades. Thankfully still much less than "a hunnert bux" here even today (hopefully not that nice Mr. Trump's import tariffs ).