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??? - float/fuel level setting - where to measure...

Discussion in 'Norton Commando Motorcycles (Classic)' started by joe czech, Dec 1, 2019.

  1. joe czech

    joe czech

    Joined:
    Feb 21, 2019
    AM I OVER THINKING THIS? setting the fuel level this AM. since the carbs are tilted up a few degrees, where is the best place to set the fuel level in relation to the float bowl edge or surface? right now, i'm pretty much at .21 inch from the front edge of the float bowl with he bike sitting level, and the carb in their natural mounted position. i'm assuming the .21 +/- .040 spec is for the carb (float bowl) sitting horizonal - or "it doesn't matter." it might be the case that the fuel level is too low in relation to the middle of the bowl as configured. comments...

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    Last edited: Dec 1, 2019
  2. Danno

    Danno

    Joined:
    Feb 7, 2010
    There are two correct float level settings; the recommended one and the one that works best for your machine. I like to set 'em nearly as high as they can go, because I don't think any harm can come as long as the floats shut off fuel flow before they hit the underside of the carbs and setting them too low will cause problems with starting and idle.

    BTW, both my Norts require choke and tickle to cold-start, so the float levels are not causing any unwanted richness. The Stay-ups are wonderful in this aspect; all you have to do is tweak the tab that depresses the float needle to change settings. I don't think I ever touched any when one had to beat the float seat back and forth in the bowl to adjust levels.
     
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  3. Danno

    Danno

    Joined:
    Feb 7, 2010
    And yes, you may be overthinking this just a bit. Nothing wrong with checking and setting by fuel level; it's what you're trying to achieve. When you get it correct, note the float levels and maybe take a pic for future reference.
     
    joe czech likes this.
  4. Danno

    Danno

    Joined:
    Feb 7, 2010
    And regardless of tilt angle, the fuel level remains the same at the center of the main jet, so that's where it should be measured, on center.
     
  5. o0norton0o

    o0norton0o VIP MEMBER

    Joined:
    Apr 27, 2015
    I don't know how you mean that, but if the float is in the front of the bowl shutting off the flow then the more you tilt the bowl forward, the higher the waterline is up front and the lower it is everywhere behind the float, including the middle... because the tilt makes the float shut the fuel off earlier when the carb is tilted forward... Fuel level changes with tilt. Shut off position of the float doesn't change with tilt.


    ... and if you set the fuel height with the bowl being level all you are setting is the "float position" where it seats the needle to shut off the fuel in reference to the "carb body". When you tilt the carb and install it, you actually get a lower "fuel level" than the level test rig shows, BUT,... the float height shuts off at the same float height because the mechanical relationship between where the float drives the needle into the seat, DOES NOT CHANGE, even though the carb is now tilted.

    As Danno correctly said, fuel height changes the quality of the idle, but that's what the idle mixing screw is for. You set the floats as high as safely possible, then use the idle mixture adjustment screw to micro adjust the mixture because fuel height and pilot jet size still have to have a fine adjustment... So you need to see the big picture of how float height, fuel height, and idle adjustment screw setting are related.

    A little lower fuel height requires a change in the idle mixture screw setting... You should be saying, "That makes sense!"
     
    Last edited: Dec 1, 2019
  6. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    You set it with the bowl level if the bowl is off the carb. If using the drain plug tube with the bowl on the bike, set it to the correct level in the middle of the carb (inline with the main jet).

    When installed on a Norton, the level will be higher at the engine side and lower at the air cleaner side. Since the pickup for the idle circuit is at the air cleaner side, setting the level at the engine side would make it too low for the idle circuit.
     
  7. o0norton0o

    o0norton0o VIP MEMBER

    Joined:
    Apr 27, 2015
    Fuel level changes with tilt. Float height (once it seats the float needle) is not effected by tilt...

    SO,.. you set the float height as high as safely possible to solidly seat the needle, and you don't worry about the fuel height changing when you mount the carbs in the tilted position because the float height doesn't change with tilt....
     
  8. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
    Just set the float level at around .040" below the float bowl lip. It will work fine with either OEM or stay-up floats. Don't worry about "fuel level." It's not rocket science and it's not a MotoGP motor. You can make yourself crazy worrying about differences that make no difference on a street bike. ;)
     
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  9. joe czech

    joe czech

    Joined:
    Feb 21, 2019
    thanks MM. since reading most of the posts on this thread, as well as a bunch of other threads on the subject, it seems like folks are setting fuel levels all over the place, so i'm guessing, it dosen't matter all that much and i'm putting way too much thought into this.

    anyway -- progress today - reset the float levels and fuel level within .1 from float bowl flange - it should get me in the ballpark. finished the rebuild on the carbs and installed w/ the Madass (Don Pender) Carb Linkage Kit. throttle cable run and everything seems to be working without issue. trial fit the air cleaner assembly - now, that was a real PITA - I think it's there to stay. finished paint work on the gas tank, and with a little luck, i'll finish up the tank and fuel lines tomorrow. hopefully, within a day or two, we'll see if I can get some life into this puppy. ;)
     
  10. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    Hopefully, I'm misunderstanding you. Setting the top of the float .040" below the bowl lip without regard to the fuel level means that you can have anything between very little fuel in the bowl and continual flooding. Also, setting the float to shut off the fuel flow when the float is .040" below the bowl lip will at least make the fuel level WAY to low for the idle circuit to properly pickup the fuel.

    Brand new AMAL carbs usually come set correctly and the top of the float is slightly above the lip of the bowl when the fuel flow shuts off and the fuel is .040 below the lip of the bowl.
     
  11. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    Within reason , it probably does not matter where the float levels are, as long as they are the same in both carburettors. When you adjust the heights of the needles in the needle jets and the main jets, you compensate for the float levels. If you are the sort of person who fits the recommended jets and measures the float levels as specified in the manual, you still usually end up doing minor adjustments to the jetting, because of fuel differences and differences in air pressures and temperatures in various locations.
     
  12. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
     
  13. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
    As has often been said here - do what you are comfortable with. If you are comfortable with the "fuel level" being set to some specific spec, then do that. If you are comfortable with setting the float level essentially as described in the OEM owners manual, do that. If you have some other method that works, then do that.

    My primary point is that the fuel level is not critical. SURE, if it's too low for the jets to reach the fuel, then that's TOO LOW; If it floods/drips, it's too high. Anything in between will work just fine. I set the float level at approx .040" below the lip of the bowl and have been doing that for many years - plastic floats and stay ups. I have no idea what the 'fuel level' is with that setting but I have never had any operational reason to care - engine runs fine under any conditions. But again, do what you're comfortable with!
     
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  14. o0norton0o

    o0norton0o VIP MEMBER

    Joined:
    Apr 27, 2015
    True BUT, a higher fuel level (rather than a lower one) helps a bike's low idle stability simply because it requires less vaccum pressure to feed fuel through the bike's idle circuit at low RPM's. (Granted that the idle mixture screw is there to compensate for that lower fuel height)

    All these guys talking "fuel height" seems pointless since the highest possible fuel height is dictated by the highest possible float height anyway, so why bother with fuel height, when that fuel height changes when you mount that carb on the tilted manifold anyway...

    Float height is better to adjust, and leave some resonable amount of space between the float and underside of the carb body so the float seats the needle strongly.
     
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