Burlen Fuel Systems are now marketing a new type of float. http://www.amalcarb.co.uk/TechnicalDetail.aspx?id=13
There's some important float height setting data on that page.
There's some important float height setting data on that page.
L.A.B. said:According to Burlen, setting the fuel level correctly is the critical part:
"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 0.25” (4.33mm to 6.35mm) from the top of the bowl."
rbt11548 said:“In this position the fuel level is correct when the top surface of the float is parallel with and just above the top of the float chamber when the valve is closed.” Is there a optimum height for the float above the bowl top?
rbt11548 said:if the height of the fuel was lower than recommended could this have an affect on the pilot screw position, for instance, to achieve the correct idle mix the recommended starting point for adjusting the pilot screw is 1 ½ turns out from seated, could low fuel level allow the mix to start getting lean sooner, say with the screws only out about ¼ to ½ a turn from fully seated?
rbt11548 said:Also, daft question time!, if the height of the fuel was lower than recommended could this have an affect on the pilot screw position, for instance, to achieve the correct idle mix the recommended starting point for adjusting the pilot screw is 1 ½ turns out from seated, could low fuel level allow the mix to start getting lean sooner, say with the screws only out about ¼ to ½ a turn from fully seated?
Corona850 said:rbt11548 said:Also, daft question time!, if the height of the fuel was lower than recommended could this have an affect on the pilot screw position, for instance, to achieve the correct idle mix the recommended starting point for adjusting the pilot screw is 1 ½ turns out from seated, could low fuel level allow the mix to start getting lean sooner, say with the screws only out about ¼ to ½ a turn from fully seated?
I can't possibly be a daft question, because I had the same question! :lol:
I put two brand-new Amals on my bike. One of the first things I did was check the floats and set them at the hitherto prescribed 0.080" below the top of the bowl. My idle screws have always been in too far, so to speak, i.e. about 1/4 - 1/2 turns out. Now, all is clear!
When I get back home to work on the bike, I intend to re-adjust the float heights per Amal's write-up and then see if my idle screw setting become more normal.
L.A.B. said:According to Burlen, setting the fuel level correctly is the critical part:
"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."
Not on my bike, and I'm about 200lb. There is still a forward tilt to the carbs.swooshdave said:Because of the angle of the manifold and once you sit on the bike, don't the carbs get level?
Corona850 said:But then - here came the revised instructions!
So, I rigged up a drain plug with a hose barb and a length of clear hose and checked the fuel level. It was about 1/2" below the bowl top with my floats set at 0.080" below.
I rigged up an old carb body and set about adjusting the float heights until the fuel level was within spec. I scribed lines at 0.17" and 0.24" below the bowl edge. Interestingly, the meniscus with gasoline seems to be about that distance.
But in the end I got the fuel level in both bowl within spec. And - what do you know? - the floats are more or less parallel with the top of the bowl just like the Burlen instruction say tehy should be. So, it seems that the INOA Tech Digest is probably correct when it says "The floats in Amal carburetors should sit 3/32" above the edge of the float bowl." All this advice about having the float below the bowl edge is incorrect for new carbs; maybe it's applicable to old carbs made with worn out tooling in the early 70s. Who knows?
Anyway, I just finished setting up my bike per Bushman's method and managed to get a nice idle at about 900rpm and no popping on overrun. A success in my book. I hope it lasts!
rbt11548 said:When you mention," I rigged up an old carb body and set about adjusting the float heights until the fuel level was within spec." could you explain a bit further in what way you used the carb body please?
Corona850 said:I thought about using water instead of petrol for safety reasons, but as the density is different I reckoned the float would 'float' more and close the needle sooner. Thousandths of an inch seem to matter here, so I used petrol. Noxious stuff and it gave me a headache, but anything for science! :lol:
swooshdave said:Meh, it's just gas.
Corona850 said:swooshdave said:Meh, it's just gas.
Obviously, you have no f*cking idea what nasty shit 'just gas' is! Do yourself a favor, educate yourself!
broken link removed
:roll:
Corona850 said:rbt11548 said:When you mention," I rigged up an old carb body and set about adjusting the float heights until the fuel level was within spec." could you explain a bit further in what way you used the carb body please?
I thought about using water instead of petrol for safety reasons, but as the density is different I reckoned the float would 'float' more and close the needle sooner. Thousandths of an inch seem to matter here, so I used petrol. Noxious stuff and it gave me a headache, but anything for science! :lol: