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

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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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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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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.
 
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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.
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!"
 
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marshg246

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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.
 
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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....
 
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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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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. ;)
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. ;)
 

marshg246

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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. ;)
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.
 
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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.
 
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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.
 
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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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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!
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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Not sure how I missed this thread.

set it to the correct level in the middle of the carb (inline with the main jet).
correct


" 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.
Fuel level makes some difference. When the fuel is set to .0XX", I always reference to the BODY..why? the main needle jet is connected to the body (via the jet holder) and is the primary distribution for above idle fuel. The needle jet length is about 1/4" long however the top of the needle/jet .107 interface is 3/16" below the carb body. That is where the fuel level belongs...+ or -

Within reason , it probably does not matter where the float levels are, as long as they are the same in both carburettors.
The idle circuit is much less affected by fuel level. Idling means the slide is closed and there is quite a high vacuum (though pulsating and sharing by the balance tube) and the idle fuel is filling the front to back passage and ready to pass through the jet into the mixing chamber (under the round blanking disc). In fact there would be too much fuel unless you open the air bleed/idle mixture adjust and let additional air in.

3. Pilot circuit mixing chamber (coloured in Yellow) – this is where the metered amount of gas is mixed with the metered amount of air and travels up into the engine through two tiny holes (mildly correct IMHO inadequate description )

Rather than to "disagree" with bushman #3: http://www.jba.bc.ca/Bushmans Carb Tuning.html
Instead let me expand the description to my understanding and extensive carb work since the mid 1970's.

The two tiny holes are:
1A. top hole is before the throttle slide and therefore @ atmosphere. It is an air supply portion during closed throttle idle that mitigates the vacuum to the fuel circuit. (coming from hole 2)

1B. top hole only acts later as a second (fuel/air mix) mix distribution once the slide starts to raise and atmosphere is replace by vacuum applied to this transition port.
This characterstic is entirely the same for throttle plate carbs as plate swings by exposing the additional holes to vacuum. Remember there is a partial vacuum all the way to the front of the slide due to the cutaway.

2/bottom hole is after the engine side of the throttle slide, and is where the 2nd air fuel mix enters the air stream.The air bleed screw is now the main air to the "mix".
However by design this circuit is now a minor contributor to air/fuel mix running the engine.




quite the rig
ROFLMAO

I'll agree the engine can run with a sloppy carb set up... ie 30 all the way to 55mpg.... start easy start hard
 
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Are you doing all this because you are running rich with darker sooty plugs ?
Change out the float needles , the needles and their jets for new.
The level in the bowls is what counts and it should be just below the carb bowl lip as stated previously, not high enough to saturate the bowl gasket with fuel . Fit new parts first. Then try again.
 

Scout63

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I just went through this and found that trial and error worked getting the level just below where the floats were too high to shut the fuel off. I could gauge too low because tickling took much longer and the bike ran hot and lean. I hope that this method is ok.
 

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