Fuel level for Amal MK1 Premier

Hi All,

I tried to adjust the fuel level of my 32 millimeter Premier MK1 between the lowest and highest values mentioned in the documentation (ie about 6ish and 4ish millemeters below the fuel bowl top edge) but could not set it higher than 8 millimeters (which is a bit too low - too weak as far as I know).
To obtain the correct value (about 5 millimeters), I have to bend the float bowl holder so much that when the carb is re-assembled, the upper part of the carb pushes the float bowl down and hence the valve is re-opened, too much fuel flows in again etc...
Am I doing something wrong or is there something else to adjust (or do I have to care about ...)?

Many thanks for your help (once again).

Laurent

That's all wrong.

The tab that you bend is the stop for the float as it pushes against the needle to close off flow. When bending the little tab in a vice cause it is tough, this will dictate were the float rest when in the stopped/top position. This position is where you measure from the top edge of the float bowl down to the top of the float. Check with Amal for the latest data.

If, of course, the carb body is pushing the float down, the neede will never seat and you are set wwwaaayyy too high.

There are more detailed and complex ways to set this height but this is the basic way.

Many thanks.

Fully with you re: how the float tab moves the needle up or down and opens or closes the fuel flow, but what is still unclear to me is that the values given by the Amal documentation (ie between about 6 and 4 millimeters) refer to the distance between the top edge of the bowl and the FUEL LEVEL in the bowl, not the top of the float.

Here is an excerpt of Old Brits web site which gives the same values as the Amal documentation:
The actual specification, from the engineer who designed the Concentric Barry Johnston, gives a gas level of between .170" (= 4,3 mm) to .240" (= 6,1 mm) below the top edge of the float bow, 170” being rich and .240" being lean. This level has a dramatic effect on the running of a properly tuned motorcycle. It pays testaments to the design of this carburetor that the range of miss-adjustment it can tolerate and still have the motorcycle run, if only poorly. It is suggested that you set the float level first before doing any carb adjustment.
The level can be estimated by placing the round edge of the plastic float between .060" ( = 1,5 mm) and .090" (= 2,3 mm) below the edge of the bowl when the needle is depressed by a slight force on one of the float's needle tangs.

Yes. 2 Schools Of Thought.
Actual Float Height At Stop,
And Actual Fuel Level At stop.

The Later With A Single Port Banjo With A Hose Running Up to Feed And The Bowl Fitted In A Vise Or The Like. This Is A More Detailed Method And Preferred.

Text Enhanced By Android.

Does this factor in the carb sits at approx 10 degree angle when mounted on the engine in the cdo?

Here is the best I've seen on Amal float levels. It was on this forum.

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

Cheers, Dan.

the bushman's site is great, this is the same idea for visual learners like myself
http://www.youtube.com/watch?v=dROb_xD200k

Ugh a shade tree expert don't need no stinking numbers to get floats right on the money or good enough it works fine. Float level only needs to be good enough the engine is responsive to air screw idle adjustment the can finer tune for fun till best idle is close to 1.5 turns out, which is the level the rest of the kit is expected to see ideally, but mostly undetectable once good enough the air screw works it treat.

hobot,
So I'm anal retentive, 27 years flying in the military does that crap to you. I am buliding an adjustable test stand in order to set the bowl fuel levels as they will set on the cdo. Will post pics when complete

Saber13 said:

hobot,
So I'm anal retentive, 27 years flying in the military does that crap to you. I am buliding an adjustable test stand in order to set the bowl fuel levels as they will set on the cdo. Will post pics when complete

Click to expand...

Here is somthing DogT built. Maybe give you and idea or two. He doesn't charge much for using his intellectual property.

amal-set-t15306.html?hilit=amal%20float%20level

Or:

L.A.B
That works also. I made one for on the bike use, not as elegant. What did you use for the 90 coming out of the bowl drain plug?

Hehe, I'm form era of long slide rules and lost a whole college grade level that might fail to pass to next class if one part per 1000 was off in calculating ideal chemical reactions and the final weights and volumes of products at the end of a long series of processes. EKG reading before the 'puter age required N th degree measures of amplitude, frequency and skews from ideal too - and tested by patient response. If ya dig in deep enough you might find the aircraft manufacturers used a trial and error process to finalize the exact measures to seek once design finalized in production and manual. I've been thru the various float level viewing methods hand held at correct angle & the site tube method to find my down and dirty works as well or better to get close to optimal level in less time too. I'll bet you still need a straight edge or other tools to get rear chain aligned - instead of just finger feeling hobot lazy way and still think its the tire that needs aligning...
Any way I"m having fun doing it my way and reading of others intensive involvements to feel like a good proper Brit Iron mechanic.

Saber13 said:

What did you use for the 90 coming out of the bowl drain plug?

Click to expand...

It's a vent elbow from a Varta battery

The fuel level in my Amals (1975 Mk3) is giving me a bit of angst........I made up a tool from an old plastic drain plug and a length of clear plastic tube, very similar to LAB's, it works well and it's easy to read. I thought I'd set the fuel level as close to 5mm below the top edge of the float bowl as that falls midway within the given values.....and by a happy coincidence, the screw flanges on the float bowl are (near as makes no difference) 5mm thick which gives an instant visual reference. I'm using the new 'stay up' floats so have pretty much immediate and simple adjustment as required.

The problem is, the carbs are tilted forwards, so a fuel level that looks good when the tube is held to the forward edge of the float bowl looks low if it's held to the rear......I admit it took me a few minutes to realise, I thought I was having a 'senior moment' a few years prematurely.

Looking at the photo of LABs fuel level tool in action (really useful reference thank you) I would read that as a little low, taking the screw flange as 5mm thick, that looks to be about 8mm below the top edge of the float bowl........but if that clear tube were moved left or right the fuel level reading would change in relation to the edge of the float bowl........ by a surprising amount given the shallow angle.

I like this method of setting the fuel level, but after an afternoons fettling my most notable achievement was fingers reeking of fuel and an ability to get the float bowls on and off in no time....I'm not sure I made any improvements though.

So my question is, how and where do you read the fuel 'level' on a carb that is angled forwards?

Mick.....................kettle738

I was faced with the same dilemma, so I made a plate that I could angle at 10% and set the fuel level at 0.17 inches at the Lower end of the bowl. When I sent them at .17 with the bowl level and installed, fuel leaked.

I just travelled about 800 miles on the Commando, during 600 of which the left float valve kept sticking and pouring gas out. This problem showed up before the trip, so I took the carb apart, but found nothing wrong. To be on the safe side I replaced the viton needle with a new Viton needle, but once out on the road the problem showed up again.

If pulling up a grade or doing +75 mph the fuel consumption was great enough that leakage stopped. If behind traffic the leakage would start up, so my on the road solution was to shut the fuel off for a bit, rather than burst into flames.
Two things surprised me- 1. How far the bike will run with the fuel off.
2. At speed, it runs exactly the same (perfect) with the fuel bowl overfull as it does just before the bowl is empty. The only poor running is at an idle when the float is stuck and fuel is gushing everywhere.
Perhaps the setting of the float level on these old or new Amals is not all that important? It seems they are not a terribly fussy instrument.
About two hundred miles from home the problem went away and seems to be gone for good. No doubt it was caused by laying the bike up for four years.

Glen

When I did mine using the DogT method with stay-up floats I didn't take into account any tilt. I don't see how you could measure it correctly if tilted - ref: kettle738 post above. I scribed a line 4mm down on the inside of the bowl and got as close as I could by bending the tab. (To me 6mm seems kind of low.) Anyway they seem to work fine.

There is nothing about tilt in any Amal directions I was able to find.

I made an correction to my comment above, When tilted 10% to match the angle of the bowl when mounted, I set the fuel level at .17 inch below the lowest part of the bowl, which is the intake side of the carb.
Chuck

I don't think the measurement is taken with the tilt.