New Amal Floats

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.

Thanks for this info, LAB.
Interesting to read about the post-1972 changes. All along, I've been diligently adjusting my floats to the 0.080" measurement, and now find out that I should have left well-enough alone!

TVMI for keeping us up to date LAB. I take it the main change inthe new model float (besides color) is the bendable tang to adjust the level? That seems like a better idea to me.

Thanks for the inf. LAB. You did answer my post on this some time ago, now I will have to go and have another play with the float levels just to see where I ended up. Being sunny and 26c. I will go for a ride first and play later.
Thanks again.
Ian

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."

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."

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Just got mail from Burlens telling me about the new floats available, I also read the info on the fuel levels and the float positions, in the 1972-Present paragraph it states “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?
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?

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?

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Yes, but as I see it, you will only discover that by adjusting the fuel level to 0.21" (plus or minus .040") below the top of the bowl?

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?

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From what I've read, I believe the fuel/float height can affect the optimum pilot screw setting.

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?

Click to expand...

It 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.

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?

Click to expand...

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.

Click to expand...

Hi Corona, like you I had set mine to 0.080", brand new carbs and pilot screw was only about 1/4 out on one and 3/4 on the other, any further out and the carbs would spit and the bike wouldn't tick over properly.
Possibly float and fuel level set too low and idle circuit not getting enough fuel which in turn only requires a small turn of the pilot screw to lean the mixture?
Could this also cause a hesitancy in pick up from idle when throttle is blipped suddenly?
I get back home on Thursday, quiet w/e, get my Christmas shopping done on Monday, then down to the shed!!!!!!
Merry Christmas to all

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."

Click to expand...

I've been working on my carbs and have re-set the floats per Burlen's directions (i.e. floats parallel to the edge, seat 0.574" below). But, as far as fuel level goes, when the carbs are installed they're at an angle, but the fuel level is - well - level. So the fuel level at the back of the carb is lower below the bowl-edge than it is at the front.

At which point should you measure the 0.21" distance below the edge of the bowl? At the front? At the back (near the pilot port)? Middle of the carb to average it? Any ideas?

Because of the angle of the manifold and once you sit on the bike, don't the carbs get level?

swooshdave said:

Because of the angle of the manifold and once you sit on the bike, don't the carbs get level?

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Not on my bike, and I'm about 200lb. There is still a forward tilt to the carbs.
Also, I found quite a variation in the other components. The two floats were different. I set the seat-depths identically, measured with a vernier gauge. One float was parallel as shown in Burlen's picture. The other wasn't. I checked out some old floats that I have and found one that matched, but also found a float slightly bigger (deeper) than the others, even though they are genuine Amal and have the same part no. (622-069). Same thing with Viton needles. Older ones have a different tip configuration, it seems. I'd never looked so closely before.

Well, as the saying goes, when all else fails, follow the instructions!
I had previouly set my floats to the 'conventional wisdom' setting 0.080" below the front bowl edge and could never seem to get a good idle, never had the air screws out anywhere near the 1-1/2 turns, and often got popping on over-run that I couldn't cure. I messed with this for a long time and was pretty close to ditching the Amals for a Mikuni.
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. I managed to bugger up one seat in the adjusting process and had to replace it. 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!

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!

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Good man!, well done!, I believe you and I had the same carb problems when set at 0.080" with new carbs so am glad to hear you got it running well.
I started the float adjustment on mine a couple of days ago but due to doing other things have not finished yet. Because I have no heating in my shed, (and it's -12 degress outside), I have been doing it in the kitchen so just using water for fluid at the moment I'll recheck using petrol later.

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?

The way I was doing mine was, I measured the fluid distance from the top of the bowl and marked it in the inside, the seat in the bowl that the brass needle seat sits in is nearly a bang on measuring point for the fluid height, I connected a feed pipe to the float bowl, I then put the bowl in a container that had some sand in it, this allowed me to adjust the position of the float bowl to ensure that the bowl was completely level while holding it secure, I know when they sit on the bike they are at an angle, but for setting up purposes they should be level. I then adjusted the levels by moving the float needle seat to the appropriate depth on each bowl until I got the fluid level correct. As I said I've still got to check it out with petrol but hopefully they will be ok.
If this is wrong somebody enlighten me please.

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?

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I screwed an old carb body to a piece of wood using wood screws and washers, then held it in the vice. I used a Christmas Puddng bowl (seasonally important!) with a hose barb glued in the bottom (using Loctite plastic epoxy) as a reservoir. The picture below shows the hook up, but with a non-drain-plug bowl. My 'real' carbs have drain plugs, so I drilled an old plastic plug and glued a hose barb into it, with some clear plastic tubing.





I marked the outside of my carb bowls by coloring in with a black Sharpie marker, then scratching the 0.17" & 0.24" levels with a vernier gauge. It's just about still visible on the photo below.



Once I adjusted my float seat I put the bowl-float assy on my carb body with the drain plug and tube installed. Using rubber bands, I held the sight-tube against the carb body. I poured some petrol into the reservoir and then watched for where the level ended up and then guesstimated if the seat needed a bit more adjustment. Trial and error, but it didn't take long.

I also used an old banjo bolt and a cut off 1/8" drill to use to raise the seat, so it was better to set it the seat a bit too deep, then use the much more controlable screwing method to adjust it back to where it should be.

Hope this explains and is useful.

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:

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:

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Meh, it's just gas.

swooshdave said:

Meh, it's just gas.

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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:

swooshdave said:

Meh, it's just gas.

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Obviously, you have no f*cking idea what nasty shit 'just gas' is! Do yourself a favor, educate yourself!

broken link removed

:roll:

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I'm not going to drink it. :mrgreen:

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?

Click to expand...

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:

Click to expand...

Hi Corona850, that's great thanks it's been a big help!, as I said, when I get the height sorted bang on with the water will use petrol to make sure it's correct.
The reason I'm not using petrol indoors is after being an operational firefighter for 34 years you get a " wee feeling" something could go wrong :wink: as we all know petrol doesn't go on fire but it's fumes will and they can travel a fair distance.
Also if I want to help science and give myself a headache, I find the golden nectar of a fine malt whisky helps a bit and it tastes a lot better
Robert

I fully agree with you about using petrol indoors. I considered water, then industrial alcohol, but used petrol to ensure the correct density fluid, as I said. I did it in my garage with the door open and a fan blowing. Still, breathing the stuff for an extended period was not smart. I should have got a proper respirator.

And I fully second the use of malt whisky. Laphroaig is my favortie, followed by Aberlour. Got some Glen Morangie too for variety.