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When I parked the TR4 in the garage yesterday I thought I smelled petrol. And yes, wet with petrol under one of the SU carburettors. Switching on the engine I saw a disturbing drip drip drip from the overflow pipe. 
So, took the lid off the float chamber and checked. Needle seems OK. Took the float out and yes, it was half full of petrol. 
Luckily I had a new one on the shelf. Three years ago I had a leak in the other float, I bought two new then. I even found the old float (I had written "leak" on it). 

What would be the cause of a leaking float? Checking both failing floats, I cannot see any pin holes or anything wrong. They are old fashioned copper or brass floats with silver soldering the two halves. 

Can chemical changes in petrol of the last years attack the soldering or the copper / brass? Is it copper? Brass? Silver solder?

Edited by badhuis
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Try droping the foats in a bowl of boiling water, it there is a pin hole you should see a steam of bubbles coming out of it.  I had one that did this and was able to repair it with a little soft solder.

You may also have a sticking float valve, so take those out and give them a good clean, or replace them.  They can be a bit of a pain!

Best regards,

Tony

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It is said that the modern petrol, with E10, eats the solder holding together the two halves of the float - and then it sinks.

Burlen can supply floats of an entirely different material which is not susceptible.

Ian Cornish

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Hio Guys,

Just had the same problem with my newly restored TR4A. Only completed several miles, luckily back on the home drive, when started misfiring. A look under the bonnet and petrol was pouring out of the front carb float chamber.  Sure enough on inspection the float was full of petrol!

I had stripped and and rebuilt the H6 carbs, which had not seen petrol since 1983, and possibly foolishly reused the original floats.

A call to Burlen Ltd made it clear that the original plastic floats are susceptible  to  modern petrol and have been superseded  by a solid  'Stayfloat style WZX1304'.

Unfortunately these are on back order with Burlen, Moss, Rimmers and others. Fortunately, managed to buy a pair from ESM Morris Minor.

Moral of this story is be aware that the old plastic floats are susceptible to deterioration from modern E5 petrol which could have disastrous consequences with petrol escaping near to the exhaust manifold.

Rich

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