Loop fuel taps

I have the original square fuel taps on my 850GT and I normally run with the right-hand tap open and the left-hand one closed. My understanding was that they only have on and off positions, so the bit of fuel in the left side of the tank is the reserve. Yesterday it started to splutter and die, so I switched the reserve tap but it made no difference. Luckily I was able to coast down to the Shell garage. I only managed to put 17 litres in, rather than the 20+ if it was empty. Any thoughts?

I do this Ian…but the only time I switched t’other tap over I got about a mile further before running out and having to call the cavalry (Guy) !
He thinks we had actually been running that tap in the on position too…
Only thing I can think of is if theres any crud in the tank it may have blocked the lower portion of the tap filter…well this happened on my old blue Le Mans…
Thus not allowing fuel to flow thro…just a thought…x

Have known this to happen.


Hi Ian, if you have been routinely using only the L/H tap, this may have given the other tap time to build up crud. How about alternating the main reserve taps from time to time?

Taps out for a clean I think. My list of jobs for the holidays is getting a bit long now.

square taps with reserve are available - I also agree with previous comments and would add that the internal fuel filter can break off/gauze crack with leads to blockage, ditto the tube.

I have also found that on my Tonti’s the double sided nut always breaks.
If the taps are available and inexpensive I would suggest renew.

In line fuel filters are not expensive and are quite small, could be hidden behind side panels?

Got round to sorting my taps out after work this afternoon. As suspected the LH tap which I use as the reserve was full of rubbish. There’s only very short standpipes on them, and a tiny gauze in the tap inlet. I suppose it stops the bits getting through into the taps or carbs, but easy to block.