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H4 Carburettor float chamber overflow


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Took the TR2 out for a ~20 mile run yesterday afternoon. Thought I could smell petrol every now and again and upon getting home found it pouring out of the float chamber overflow on the rear carb.

I took the lid off and found the needle valve had jammed fully open. Of course lifting the lid off allows the needle to drop, but I believe this was the cause of the overflow. It lifted OK by hand, but I think that on full travel in the open position it jams sufficiently for the float not to be able to lift it.

I reassembled holding the needle up with a thin screwdriver as I did it and all seems fine, but I'm wondering if there might be the risk of it jamming again. Could it be due to wear in the needle valve allowing it to jam or drop too far? Any thoughts or advice gratefully received, as ever.

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Thanks Stuart.

The Moss and Rimmer part number for the needle valve and seat kit is WZX1101a, but it seems to be out of stock with those suppliers. I've found the same part number listed for the early MG Midget and other cars, and in stock at suppliers for those cars. I assume it is the same item?

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Thanks again.

I looked on their site earlier and couldn't find the "Moss" part number. I suspect it is VZX1101 on the Burlen site - http://sucarb.co.uk/float-chambers-spares/needle-valve-kits/standard-needle-valves.html

Listed as 0.096"

...but they are also out of stock. I've sent them an enquiry to check

Rod

 

Edited by Rod1883
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Thanks Nigel.

Yes, the floats are the old ones, and they float. I always use Millers VSPe plus ethanol treatment and fill up at our local Power fuels filling station which sells zero ethanol unleaded whenever I can so hopefully they will continue to last....

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I popped over to Southern Carburetters at Crawley on Thursday and picked up new needle valves and seats, plus float chamber lid gaskets and new fibre washers for the connecting banjo's. Very impressed with the set up and knowledge there.

All fitted , but due to our drive being dug up mid replacement I haven't yet been able to road test.

Whilst I was at Southern Carburettors I had a chat with Roy there who was very helpful and I picked up new mixture needle adjusting screws with incorporated o-ring and new star washers (plus new diaphragms) for the leaking air valve damper tubes on the Stag (see my post in General technical)

Edited by Rod1883
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A similar problem I am having with the carbs flooding after a week or so standing idle. I have fitted the Grosse jets and everything is fine in normal use, but after a week or so of not being started the back carb invariably starts flooding from the overflow and can only be stopped by removing the float lid and re fitting it. 

I suspect that the fuel left in the float bowl is evaporating away allowing the float to drop right down, and then when the engine starts again, which usually takes a bit of cranking to get the fuel through, the jet fork must be preventing the float coming back up, hence thje flooding. Taking the top off allows the float to pop up and then all is OK again till next time. The floats are brass and do float OK.

Anyone else had a similar problem?

Ralph

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2 hours ago, Ralph Whitaker said:

A similar problem I am having with the carbs flooding after a week or so standing idle. I have fitted the Grosse jets and everything is fine in normal use, but after a week or so of not being started the back carb invariably starts flooding from the overflow and can only be stopped by removing the float lid and re fitting it. 

I suspect that the fuel left in the float bowl is evaporating away allowing the float to drop right down, and then when the engine starts again, which usually takes a bit of cranking to get the fuel through, the jet fork must be preventing the float coming back up, hence thje flooding. Taking the top off allows the float to pop up and then all is OK again till next time. The floats are brass and do float OK.

Anyone else had a similar problem?

Ralph

TBH I would replace the Grose valves and fit the normal valves as they dont suffer tis problem, also if the car isnt started for a fair time then its always better to use the priming lever on the pump to fill the float chambers.

Stuart,.

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