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E: Engine Amal Mk1 Premier Carb - Float Level

MartynG

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VOC Member
Any opinions on what is the correct float level with a Amal Mk1 Premier concentric fitted with the 'new' stay up float and how to set it?

I tried setting it with the top of the float 0.080 below the top edge of the float bowl but the problem us that the top of the float is NOT level. With the edge furthest from the float pivot 0.080 below the bowl edge, the edge of the float adjacent to the pivot is ABOVE the bowl edge and actually holds the float down resulting in the float needle being held open when the carb is assembled.

So I kept adjusting the float level till I got to the point where the float needle actually closed once the carb was assembled.
 

MartynG

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Found the answer myself on the Burlin Web Site. here it is

The correct fuel level for all Mark 1 Concentric carburetters is 0.21" plus or minus 0.040" below the top edge of the float bowl. Thus when the needle valve is being held shut by the tangs of the float, the level of the fuel will be between 0.17" to 0.24" (4.33mm to 6.35mm) from the top of the bowl.

The fuel level can be checked by removing the float chamber and observing fuel running into it. The fuel flow should be sufficient to hold the needle valve open, until closed by the action of the float. Insufficient fuel flow will cause the needle valve to seal under its own weight, before the float rises far enough to press the valve shut. The level of the fuel can then be measured down from the top surface of the float chamber.

The fuel level can also be checked by attaching a piece of clear tubing to the bottom of the float chamber. A plastic float chamber drain plug can be modified to mount a suitable spigot, such as an old jet, to attach the tubing. Route the tubing in a vertical position alongside the float chamber, then open the petrol tap and fill the float chamber with fuel. If the fuel level is in the correct range, the fuel will rise in the tube to a point between 0.170" and 0.240" , below the top edge of the float bowl. Start the engine and ensure the fuel level remains within the correct parameters.

The new Amal 'Stay Up' float has stainless steel tangs which can be bent to alter the fuel level. The tangs can be easily adjusted, by clamping the float in a vice up to the spindle hooks and tapping the body of the float gently in the direction required until the required level is achieved.
 

MartynG

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VOC Member
I think they are saying a bit higher now, But I was playing with a stay up float the other day, And if you bend it too much, The valve hardly opens !!, Very Tricky. Cheers Bill.
I rigged up a sight level using a plastic float chamber drain plug, an old jet and some clear plastic tube. I put 2 scribe marks on the outside of the bowl one 0.170" from the top edge, the other 0.240".

After 2 attempts at setting the level it is now very close to the top mark. Yes Bill, very tricky.
 
Last edited:

Chris Launders

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VOC Member
I was having fuel starvation problems with a MK1 last year and ended up calling Burlens, they told me the edge of the float away from the needle should be level with the edge of the float chamber, this still didn't lift the needle off it's seat properly, the float was fouling the chamber before lifting the needle off it's seat, it was a brass/viton needle to which I was told that these are too heavy for modern fuel to lift off the seat enough under fuel pressure alone which is why they now supply alloy/viton float needles.
 

vibrac

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Makes you wonder if pre monoblock top or bottom feed float chamber needles are too heavy the bottom feed with that relatively big taper must weigh a lot more than a monoblock needle
I know I have had a devil of a job with my cammy velo spraying out the ethanol poison as can be read in previous threads
 

vin998

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VOC Forum Moderator
Makes you wonder if pre monoblock top or bottom feed float chamber needles are too heavy the bottom feed with that relatively big taper must weigh a lot more than a monoblock needle
I know I have had a devil of a job with my cammy velo spraying out the ethanol poison as can be read in previous threads
I suspect the weight of a pre monoblock needle will not make any real difference. It is the total weight the fuel has to lift which is the needle and float combined and with the Mk1 concentric always using a plastic float then Amal have had to make the new float out of ethanol resistant plastic. I believe the new Mk1 floats are also not hollow, but more a honeycomb inside and so weigh more so to compensate the needle has to weigh less. The restricted area the float operates in a MK1 doesn't allow for different size (larger) float to get the same buoyancy with the modern fuel so its all a compromise.

The float chamber in a pre monoblock has a lot more room (height) so it is easier to use a "modern" plastic float which may be a different volume.

Simon
 

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