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Main fuel tap standpipe

Discussion in 'Norton Commando Motorcycles (Classic)' started by Danno, Jul 12, 2019.

  1. Danno

    Danno

    Joined:
    Feb 7, 2010
    Can anyone tell me what the purpose of this is? Drained the Titanic's tank to put in some fresh 93 octane no-eth and I noticed more than an inch of fuel (a quart or so) left in the right side of the tank, while the left side (reserve) was completely drained except for a trickle left where the top of the tap stands proud of the bottom of the tank. The standpipe doesn't appear to be taller than the rear of the tank tunnel, so no way for any of that fuel to get into the lines. Unless there's a good reason I can't fathom, the pipe has got to go.
     
  2. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
  3. Danno

    Danno

    Joined:
    Feb 7, 2010
    Thanks, Les. I don't believe that removing the pipe could somehow affect reserve capacity and I don't ever want to have to desperately tilt the tank. I can see where some of the fuel from the right could splash over to the reserve side in motion, but it has to be minimal. I got more than 2 1/2 gallons out of the main tap and another 1/2 gallon from the reserve, so there was at least a quart of fuel that can't be utilized.

    I know you can run it either way, but I've always put the main tap on the right and the reserve on the left so it could e easily opened while rolling when the carbs start sucking wind. If you run out and for some reason you can only get a small amount of fuel (not enough to make much reserve) I would prefer to be able to use it all.
     
    Last edited: Jul 12, 2019
  4. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
    FWIW - on my Fastback tank I discovered the same thing. On my FB tank, once the fuel level drops to a certain point, there are essentially two separate fuel tanks with no 'connection' between them under normal conditions. So I installed reserve petcocks in both sides and use the right side as the main and the left as the reserve. Works great - there is a bit over 3 quarts of fuel left when I open the left side.

    Don't know if the same sort of tank 'separation' exists on Roadster or Interstate tanks.
     
    Dommie Nator and Mic like this.
  5. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    I use a reserve tap both sides on my Roadster.
     
  6. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Draining the tank statically, the amount of trapped fuel will be more than if you were riding.
    If you fit two reserve taps to a Roadster tank then don't expect to get too far on that 'reserve' fuel supply.
     
  7. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    I don't expect to get really far even on a full tank.
    I know what you mean though as fuel splosh will reduce the theoretical amount from no difference to less.
     
  8. kommando

    kommando

    Joined:
    May 7, 2005
    The tank shape is different but 2 reserve taps on a 1969 TR6 home market tank will give you a reserve of 1/4 mile, luckily I was on the top of a hill with a filling station at the bottom. A standpipe got added when the tank was low again a couple of days later.
     
  9. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    I've done about 10 but I found a garage before I ran out.
    I feel an experiment coming on...
     
  10. Danno

    Danno

    Joined:
    Feb 7, 2010
    I wouldn't deny that, but I having unused fuel in the tank won't extend your range. Quite the opposite.

    I've always done static drain tests on my bikes just to get an idea of the capacities. Many riders have no clue about their actual fuel range or mileage and some (my Harley-riding buddy) freak out when they hit reserve because of that ignorance. If I rode these old crocks any distance, I'd run 'em down to empty while carrying some spare fuel to see more precisely how far they'll go. I know
    because of the tank shape, the SS clone has a very small reserve. The Titanic's Roadster tank is baffled and I assume that's to minimize splash and keep the fuel on the side it started on.
     
  11. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
  12. Danno

    Danno

    Joined:
    Feb 7, 2010
    I have two like that, but with a pretty precise gauge on my KTM, I know when the light starts flashing, I have a gallon (40 miles) left.

    I rode the ZX-14 down to fumes once in Oklahoma, getting 10-15 miles more than I thought I could and when I filled it up, it took 6 gallons to fill the 5.8-gallon tank.:oops:
     
  13. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    I wasn't suggesting it would extend the range, with two 'reserves' you will travel further on 'main' supply and not so far on 'reserve' but with the stand pipe it's easy enough to lean a relatively light bike like a Commando over far enough to slosh the trapped fuel to the reserve side. Edit: Or, remove the tank and tip it.
     
  14. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    That experiment then:
    Roadster tank fitted with two reserve taps, I run the right hand side tap normally with the left hand tap being my "reserve reserve"
    I ran the bike on A and B roads with plenty of turns and stops to get some splosh over from left to right whilst it was running down on the right hand side.
    First falter I switched the left tap on and pulled over to take a picture.
    Set off again until it ran out, second picture.
    As I knew I had about three litres of fuel tucked away behind me I wasn't being frugal so I "might" have got slightly more mileage.
    Result: A tad under 9 miles.
    20190713_125458.jpg 20190713_130926.jpg
     
    Last edited: Jul 14, 2019
  15. Tornado

    Tornado VIP MEMBER

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    Dec 5, 2017
    Cool! Now we need you to do it, exactly same run, with a standpipe setup to see what difference it makes ;-)
     
  16. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    It shouldn't in theory be different, however there would be some fuel left in the standpipe side to splosh over to the reserve side.

    ...and, no, I'm not going to prove it.
     
  17. Danno

    Danno

    Joined:
    Feb 7, 2010
    One question, Nate, was the tank baffled or no?

    The owners manual for the Simplex Servi-Cycle (1935-1952 divided tank, one petcock) advised the owner who had run out of fuel to lay the bike on it's side to allow the half-gallon on so on the opposite side to slosh over to the side with the petcock and be on your way. Not too difficult with a 135-lbs machine.
     
  18. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Does anyone use a 3 position reserve type tap? The positions are On, Off, Reserve.
    These have a standpipe perhaps 2 or 2&1/2" long and bring fuel in from the top when in the "on" position. In the " Reserve" position fuel flows in around the base of the standpipe.
    This way you have a decent reserve amount but also get full range from the tank.
    I used one of these on the Special, Pingel brand as high flow was needed. 30 miles on reserve but it's a fairly big tank, 19 litres.

    Glen
     
    Last edited: Jul 14, 2019
  19. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    15632173135758219611027743118591.jpg
    I can't see any baffles.

    Edited, yes, if these are they?
     
    Last edited: Jul 15, 2019
  20. kommando

    kommando

    Joined:
    May 7, 2005
    I use one on a B44 Victor Special tank, works well and the tank is nearly flat at the back so the one tap gets to nearly all the fuel. Using Two with a tank that traps fuel on one side would work.
     

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