Bike is a 79 T140 with Mk 2 Amals. I changed out the carb to head rubber couplers and have the air filter covers off. I turned the gas on to check the fuel line to carb connection for leaking and after several minutes gas started coming out of the throat of the carb. Is this a problem. I always turn the gas off when I turn the bike off after riding so I do not know if it normally happens with my bike. Should the float closing the rubber tipped needle overcome the gravity pressure? Thanks
Mk 2 Amal flooding
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11,429 Posts
It could be....
The gaskets are a bit misaligned and the float is catching - trim the gasket and take care building it back up
The floats are past it- buy "stay up floats" which are ethanol proof
I run ethanol free (shell V power or BP super) but still use the stay ups
The gaskets are a bit misaligned and the float is catching - trim the gasket and take care building it back up
The floats are past it- buy "stay up floats" which are ethanol proof
I run ethanol free (shell V power or BP super) but still use the stay ups
Fess up time. I disassembled the carbs and ran them through an ultra sonic cleaner. Could the brass/bronze seat that the needle sits on become dislodged slightly and allow gas to bypass the needle. The seat is not shown on any of the diagrams that I have but it is obviously an insert. The tops of the inserts are slightly proud of the bowl. I was thinking of using a punch or wooden dowel that fit inside the insert to make sure it is in all the way. Is this a good or bad idea?
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3,501 Posts
Hi Thomas,
The brass insert can be moved up or down to alter the float height, that is the theory anyway-in practice you just destroy them on the mkII Amal (the mkI seems ok to move), the mkII just seem a lot tighter and a lot more fragile-not the best combination.
I have never managed to move one successfully, just mangled them, then had to buy new float bowls as the brass inserts are not available separately (unless someone else knows a source).
The float assembly seems particularly finicky about having everything centralised before reassembly, oversized gaskets can rub against the bowl, preventing it from fully sealing.
If you find your float levels require adjusting, it is far easier to ditch the plastic float and fit modern stay up floats that have an adjustable tang.
Just to re-emphasis do not be tempted to hit those brass inserts, even if the bowl is heated--unless someone else has found a technique to do it, and can share it with you on the forum.
Regards
Peg.
The brass insert can be moved up or down to alter the float height, that is the theory anyway-in practice you just destroy them on the mkII Amal (the mkI seems ok to move), the mkII just seem a lot tighter and a lot more fragile-not the best combination.
I have never managed to move one successfully, just mangled them, then had to buy new float bowls as the brass inserts are not available separately (unless someone else knows a source).
The float assembly seems particularly finicky about having everything centralised before reassembly, oversized gaskets can rub against the bowl, preventing it from fully sealing.
If you find your float levels require adjusting, it is far easier to ditch the plastic float and fit modern stay up floats that have an adjustable tang.
Just to re-emphasis do not be tempted to hit those brass inserts, even if the bowl is heated--unless someone else has found a technique to do it, and can share it with you on the forum.
Regards
Peg.
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11,429 Posts
Hi,
Hth.
Regards,
Hmmm ... doubt it somehow; ultrasonic carb. cleaning is very common, never seen anyone else post the seat has "become dislodged slightly and allow gas to bypass the needle". Simple to check - assemble floats, bowls, needles, pivots, pipes, blah - but not the bodies, jets, etc., connect everything to the taps and turn 'em on; the bowls will fill will fill with fuel, you'll be able to see whether the the offending float and needle stop the fuel before it overflows (obviously have something under the bowls to catch any overflow, plus it'll be somewhere to empty the bowls after you've tested). If the floats 'n' needles stop the fuel when they should, you'll know the problem is something like a gasket when you assemble the bowls to the bodies?
Hth.
Regards,
I did not know of that method of checking the float and needle. Simple and obvious when you know it, now I do. Thanks Stuart and everyone else. Having used said method I now know that I have one bad float. I am going to get a "stay up" float.
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3,501 Posts
Hi Thomas,
Once you have your new float(s).
Gently grip the float bowl in a soft jaw vice, assemble the float/needle/pin, and hold the locating pin in position with two fingers on one hand. Using a pointy tool (small scsewdrver/centre punch. etc.) Press down on the tang that locates the needle (not on the needle itself) until the needle seats. The top of the float should sit parallel to the top of the float bowl (just to be clear,not the same height, just parallel) . If it is not parallel adjust the metal tang until it is.
If you bought two floats set the other side the same. If you bought one float, check the original plastic float has the correct alignment, if it is not correct, buy another adjustable stay up float, and adjust it.
Regards
peg
Once you have your new float(s).
Gently grip the float bowl in a soft jaw vice, assemble the float/needle/pin, and hold the locating pin in position with two fingers on one hand. Using a pointy tool (small scsewdrver/centre punch. etc.) Press down on the tang that locates the needle (not on the needle itself) until the needle seats. The top of the float should sit parallel to the top of the float bowl (just to be clear,not the same height, just parallel) . If it is not parallel adjust the metal tang until it is.
If you bought two floats set the other side the same. If you bought one float, check the original plastic float has the correct alignment, if it is not correct, buy another adjustable stay up float, and adjust it.
Regards
peg
New float and needle installed and the bowl still over flows. I adjusted the float but it still does not seal the needle. I am going to replace the float bowl next. Questions, does anyone in the USA sell these? I did a quick web search and couldn't find one except from Amal in the UK. Does anyone have any other suggestions or ideas. As far as adjusting the float, when I installed it out of the box it was already parallel to the top of the bowl and it didn't seal so I adjusted it so that the float is not quite up to parallel so it is definitely "pushing" the needle down. This adjustment lowered the fill height and slowed down the time that it takes to overflow but it still happened.
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3,501 Posts
Hi Thomas,
There is one trick you might try before getting a new float bowl.
Sometimes a needle can hang up on the inside of the seat, so to eliminate the chance of friction in this area holding the needle off the seat, or not allowing the float pressure to fully seal it, try this:
Get some metal polish and some Q-tip's.
Put A q-tip in a dremmel (or electric drill) place a dab of metal polish on the q-tip cotton wool.
Then polish the inside of the brass insert, the polish will go black very quickly and the inside of the insert will gleam like a mirror.
Next take the needle, you will see three edges on this, hand polish these edges.
Clean up all traces of polish.
Place the gasket on the bowl with the 4 screws pushed though from the top to hold it in place.
Trim any excess gasket off with a razor blade that hangs over the inside edge of the bowl.
Assemble the float/needle assembly, adjust float back to parallel. Fit the bowl to the carb, cross your fingers and switch on the fuel tap.
regards
Peg
There is one trick you might try before getting a new float bowl.
Sometimes a needle can hang up on the inside of the seat, so to eliminate the chance of friction in this area holding the needle off the seat, or not allowing the float pressure to fully seal it, try this:
Get some metal polish and some Q-tip's.
Put A q-tip in a dremmel (or electric drill) place a dab of metal polish on the q-tip cotton wool.
Then polish the inside of the brass insert, the polish will go black very quickly and the inside of the insert will gleam like a mirror.
Next take the needle, you will see three edges on this, hand polish these edges.
Clean up all traces of polish.
Place the gasket on the bowl with the 4 screws pushed though from the top to hold it in place.
Trim any excess gasket off with a razor blade that hangs over the inside edge of the bowl.
Assemble the float/needle assembly, adjust float back to parallel. Fit the bowl to the carb, cross your fingers and switch on the fuel tap.
regards
Peg
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2,188 Posts
Why do you think its the float? Does it have a hole or crack and allows fuel inside the float? Did you check to see if your needles are seating all the way? Are they worn at all?
Or it could be that the seat is marked or worn in the bowl.
I think it would be a good idea to start swapping needles and floats around between bowls and see if you can isolate the issue first.
If the bike has been severely neglected or has high mileage on it then sometimes replacing all [bowls, needles, floats...as a complete 'kit'] can help.
I'd also replace the seals in the choke setup...which is a really a flooding bypass and not a real/proper choke as we often see it [but these are in the carb body and not related to your issue.
Or it could be that the seat is marked or worn in the bowl.
I think it would be a good idea to start swapping needles and floats around between bowls and see if you can isolate the issue first.
If the bike has been severely neglected or has high mileage on it then sometimes replacing all [bowls, needles, floats...as a complete 'kit'] can help.
I'd also replace the seals in the choke setup...which is a really a flooding bypass and not a real/proper choke as we often see it [but these are in the carb body and not related to your issue.
Problem fixed. A friend of mine had a 3/16" spherical cutter which he put on the seat and gave it a few rotations by hand and it basically cut a new seat. Prior to doing that I did check to see if it was cracked but everything pointed back to the needle not sealing. All is well again. Thanks for the suggestions and input.
Finally sussed out the persistent flooding in one of my two Mk2 Concentrics. Tried the usual remedies – dozen of rebuilds, ultra-sonic cleaning, new float needle, new float, stay-up float etc… no difference. Light bulb moment came when I realised that the little ends of the float bowl gasket are meant to sit OVER THE TOP of the float shaft. With repeated rebuilds these gasket tabs either bend, fall off or get pulled off as outwardly pointless, when in fact, they have a vital function of holding the float bowl at the right level to allow the needle to do its work. Pulling the tabs off allows the float shaft to rise up an extra couple of mm when the bowl fills up, rendering the function of the needle useless!!! Fit new gasket (or an old one with the tabs still in place). Bingo. So Zimples!.
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