MGB Register Forum

Has anyone else experienced problems with float needle valves? I have just fitted a pair of new needle valves from Moss. They are of the 'soft tip' type, rather than the existing metal tip type and I have replaced both needle and seat. Both carbs have refused to seal. Initially it was just the back carb that leaked, I contacted Moss who promptly sent me a replacement, but before I got a chance to fit it (I had already re-fitted the original seat and needle as I needed to use the car) the front carb also developed a leak. In general I have always found stuff from Moss to be pretty good and these parts are UK made, so I'm surprised that both are leaking. I am now going to put my original needles and seats back and hope they seal enough to use the car for a 150 mile trip I have to make tomorrow! Has anyone else had any problems?

Mike, these needles and seats were fitted by me in my BGT a few years ago and have always worked fine.
I guess yours could be a bad batch or a cheaper more recent batch?
Other possibilities might be the float height setting not adjusted correctly? Could be different from the original needles?
Did you have any particles or dirt in the float chambers when you looked in there?
Were the floats in good condition, and airtight?

You probably have thought of all of these options so apologies if you have!

Ian F

Hi Mike
You don't give the year of your car, but are you sure you have the correct float needles as there are 3 types? See here http://sucarb.co.uk/float-chambers-spar ... -kits.html
I would also suggest a call to Burlen to see if they can help. The phone number is at the top of the page for the float needles. Ask for 'Technical Advice' - they are very helpful!
Generally, I would also advise people to overhaul the fuel system to make ethanol proof by fitting an inline fuel filter close to the carbs to stop debris from the fuel lines and tank getting stuck under the needle valves, and if the flexible fuel lines haven't been changed in the last 5 years the change them so you are sure they are ethanol proof. The diaphragm in the pump is also vulnerable to ethanol and again if the pump has not been changed recently then either change the whole unit or replace the diaphragm. Overhaul kits are available from Burlen.

Thanks to everyone for your helpful replies. Moss have refunded my purchase price plus a small compensation. In the meantime I have re-fitted my original float needles and so far there has been no leakage. I will keep a careful watch on them and see how things go. If they leak again perhaps I'll try the moss ball bearing upgrade.
I have anew post about SU carb needle profiles, any advice appreciated.

Mike, what's this Moss ball bearing upgrade? Can't find anything on their site.

Hi Vic
They are the Grose Jets - I think!
Part No. GAC9201X

Thanks Peter, I'll have a look.

It may be that your floats are worn and not pushing the pins in a vertical axis. I corrected the issue by removing the pins and fashioning a bearing from the aluminium top of a Coke can. Cut a rectangle of Ali with scissors to fit between the metal lugs and wrap it around the brass spindle to just the right length (it may take a few attempts!) Once done choose a twist drill and use it between thumb and forefinger to drill out the nylon lugs to accept your Ali bearing. 40 years on, still the same floats (the needle valves have been changed a couple of times though)