ES2 Amal 276AU/1BE Leaks -

Previously Josh Fribley wrote:

I have a brand new Amal 276AU/1BE carburetor that leaks like niagara falls. LOL. The leak comes from the bottom of the carb body. The leak emanates from the mixing chamber union nut. The jet block is fully seated in the carburetor body. There is a jet block washer in place between the bottom of the jet block and the mixing chamber union nut. The leak seems to come from the poke yoke slot and the jet block. I do not believe the problem is with the remote float bowl. The float needle position is in the bottom slot. The float is plastic and there is no leak in the float because I can shake it and it does not have gas inside. I have been chasing this issue on and off (ie time permitting) for a year. I would really like to get my restoration going this year. Any and all feedback is welcome. I am starting to think Mikuni to make thing simpler.

Thank You.

Josh Fribley

Columbus OH USA

Hi Josh - Not certain what a "poke yoke slot " is . Why don't you give me a phone call - talking is faster and easier than typing for me - I am in NJ and have a 1950 ES2 with original 276 - if you have ES2 parts book ( mine is Main-Smith reprint ) or Amal exploded diagram it would be helpful.

My number is 609 384 3800 - available to 10 pm tonight - hope I can help - ( Mikuni - yikes ! )

Is this a new Burlen Amal carb ? If so, it works on the principle of the 'R' suffix carbs used on other makes and slightly different from the original Norton carbs which dribbled out of the inlet if flooding.

On the 'R' carbs, the slot above the mixing chamber nut acts as an overflow. If the float shut-off is functioning correctly and the float level set appropriately, fuel cannot leak out of this slot as the maximum level is lower.

I think that you have to go back and look at float chamber function It doesn't take much dirt or dust on these brass-to-brass needles and seats to cause a problem. If your fuel tank is producing any sediment then the problem will be persistent.

What length of mixing chamber nut do you have ? The ES2 normally has the long nut - a typical 'side-valve' short nut will raise the float level considerably. An extra washer here will drop the level.

It's quite OK to remove the float chamber cover and have a look at what's happening with the engine running.

I take it that the carb is exactly vertical ?

It seems that Richard ( Payne - not me ) is offering sound advice. My suggestion would have been that flooding may not be the issue as the raw fuel would be coming out the inlet as he mentioned.

Looking at it now knowing about said slot acting as an overflow it seems it may be flooding .

You might try disassembling /cleaning the float chamber and lightly lapping the valve / seat with fine polishing compound but this should not be necessary on a brand new unit.

IIRC the top cap of the float chamber acts as a guide for the upper end of the float valve to keep it concentric with the seat so I don't know if the carb will function with it off - perhaps this is different on the new ones. With this in mind , the valve will not seat and stop fuel flow if the top of the valve is not in the correct position. Also check that all is well with the clip that connects the float to the valve.

The hard fiber washers need to soak and swell a bit to do their job and stop leaking and the manufacturing process may have left some swarf that could cause problems.

If fuel sediment is suspected try running or fueling the carb from a temporary new and clean source.

Again , feel free to phone and keep us updated - Richard

Richard - they do run with the cover off of the float chamber - in fact if you lose one, you may not notice ! The depression of the float as the valve opens is actually very small.

Norton were the first make to use the 276 and for some reason they stuck with it, even when a new version was introduced that other manufacturers adopted. The photo below shows a Norton 276 body alongside a 276R from a BSA (ignore that the setting screws are opposite-handed).

You can see that the locating slot on the original Norton-type mixing chamber is much shorter and doesn't come above the level of the jet block It cannot flood from there as the block is a tight push-fit in the mixing chamber. Any flooding will dribble / spray out of the inlet or into the engine. This probably explains the characteristic Norton blow-back circle on the front of the oil tank

The current production Burlen carbs are all of the later 'R' (revised) type and I assume that if Josh's carb is 'brand new' and not NOS, it will be of the later type...On these, any excess fuel entering the mixing chamber will drain from the extended slot and no amount of tightening will prevent it.

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Richard - Thanks for sharing your knowledge and I would hope our discourse will not be construed as an attempt to Hijack Joshes' thread . Learning is what it is all about . Regarding spitting/blowback I would assume that the overlap in valve timing has much to do with it before the optimum RPM for positive gas flow is obtained.

Hi

As you have the plastic float, you should have the float needle with 2 slots for the float. The lower slot is for the plastic float and the upper one is for the brass float. If it is located on the top slot the float level will be too high.

Paul

Sadly another example of poor quality control with the new AMAL carbs, Iâve had 2 and theyâve both had issues. One (concentric) had swarf in the pilot circuit and the other (monoblock) has a sticking slide which was only cured by fitting the old jet block.

Is it leaking from the large union nut at the base of the carb body?

I had similar grief with my 48 ES2. Inside the nut is a fibre washer and it was leaking past this. I cured it by smearing the faces with Blue Hylomar gasket sealer. It is petrol proof. Has been working for at least three years so far.

I do the same but with Wellseal. Applied with a brush, left for 15 minutes or so before assembling then left for 24 hours or so before filling with petrol.

I've started to use this technique on all fibre washers as the ones available these days seem much harder than they used to be.

Late Spring Bank Holiday, Josh, in UK.

This does not inspire confidence in light of the fact that I just dropped a bundle on a pair of new 932 Premieres for my Combat Commando and I am a long ways off from installing them.

Nothing to do but wait and see and keep the originals I suppose.

Fingers crossed- Richard