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MG MGA - Fuel leak from bottom of carb

Hi my MGA has developed a Fuel leak from the bottom of the carb.
At first I thought it was from the bottom of float chamber, but thats OK and float valve is OK. Its coming from the bottom of the jet assembly. Has anyone else had this problem ?
DJ Joy

Yep, very common. Just need to replace the jet bearing kit.

Moss Motors P/N 370-395 (over here in the States) or check http://www.sucarb.co.uk/CarbEssentials.aspx?ProductId=9956 for the gasket kit.

Gene Gillam

Thanks Gene, Do I have to remove the carb, or is it possible to withdraw the jet assembly in situ ?
DJ Joy

Quite fiddly down there in a confined space and you need to disconnect all the levers. Probably easier to do it on the bench.

Steve
Steve Gyles

Chuckle. If you are a bit of a contortionist you can R&R the float chambers to change the rubber grommets. I know this is not your (current) problem, but it may help for access to the jet parts. The gland nut is likely a lot easier for access if you remove the air cleaners first. Then disconnect the choke linkage before removing the gland nut on bottom. The jet seal parts are small and fiddly, and by that time you have it mostly disassembled anyway, so I recommend that you take the carbs to the work bench before disassembly. Remember you also have to center the fuel jet during reassembly.

The original cork jet seals or modern rubberized cork seals are often fickled. Sometimes they stick or leak. Polishing the OD of the jet should help. Soaking the seals in oil before assembly should help. If you park the car for several months (off season) the jet seals can dry out, after which they may stick and/or leak, and you get to start all over. If it only sticks you might disconnect the choke linkage, pull the jet out, polish it clean, oil it, reassemble everything, and it may work again.

My favorite cure for all this is to replace the original jet seals with Teflon O-rings, two O-rings in place of each jet seal, eight O-rings required for two carbs. I have done this for several cars, and many other people have also done it. I have never hear of any sticking or leaking with the Teflon O-rings. Mine has been in service with Teflon O-rings for 15 years and 125,000 miles no stick and no leak. The Teflon O-rings seem to last longer than the brass throttle shafts, and they are cheap. See here: http://mgaguru.com/mgtech/carbs/cb106.htm
Barney Gaylord

I don't think you will manage to remove the jet bearing assembly in situ as the space is very restricted. IMHO fitting new cork seals with the carbs in place is practically impossible.

Frank
F. Camilleri

Do as Barney suggests and replace with the cork jet seals with teflon O-rings especially if you are using 95 octane unleaded here in the UK with its 5% ethanol. The o-rings' UK reference is BS.10. You may need other SU seals to complete the job so before getting the O-rings, it may be worth asking if the current seals are actually ethanol proof yet.
Pete
P N Tipping

Pete
Where did you get the specific O rings in uk?
Bruce
Bruce Mayo

Barney,

The Teflon seals you used, are they O rings or Teflon Back-up rings?

I think you mean the (endless) ones on the attached link.

http://www.claron.co.uk/pdf/f4.pdf

Part No BS 010/E

Is that right?

Paddy
Paddy Reardon

Bruce - I got them at a local seal supplier, Flowseal, Waterlooville, Hants. As seals go there is nothing special about them and should be readily available.
Paddy - They are just the same as rubber o-rings but in teflon. It can be written different ways i.e. BS.10, BS.010, BS-010 but nominally 3/8" O/D x 1/4" I/D. I got 2 sets (x16) for £6 to cover a minimum order value.
Pete
P N Tipping

Bruce - the seals came from Flowseal, Waterlooville. 2-sets (16) £6 min order.
Paddy - they are not back-up rings they are standard O-rings - to BS.010 or BS.10 in teflon.
Pete
P N Tipping

This thread was discussed between 16/12/2012 and 20/12/2012

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