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MG MGB Technical - Bleeding ZS Carb?

Recently i suffered the humiliation of breaking down on the main street of my town in my little jalopy.

A quick call to the garage tells me that the problem is the carb is out of oil. Fair enough, i have a bottle of mystery oil in the trunk so i put some into the carb and off i go again.

Now. How quickly should the oil in the carb dissipate? I know there's supposed to be pressure when you screw the cap back into the carb, but when i opened it this morning to test the level, there was no pressure at all. Bearing in mind i put oil in the thing less than a week ago, i'm guessing i should be worried.

The area around the carb looks dry, so i'm guessing it's not leaking anything directly from the carb, but as an almost complete MG newbie, i wanted thoughts on how i should proceed...

Should i even bother having the huge costs of having some mechanic charge me a billion dollars an hour on labor just to trace a leak? Or should i spring the 350 bucks and get a brand new Weber?

Your thoughts and ideas are appreciated.
Chris

Chris. Due to the design of the Z-S carb, the oil can leak out if the rubber O ring is bad. Most leaks can be cured by renewing the O ring. The oil leaks past the O ring and down into the throat of the carb being drawn into the intake manifold. A replacement O ring is an inexpensive replacement which may cure the problem. Long term, I would prefer either twin SUs or a Weber. Les
Les Bengtson

Chris, check the midget technical archives for
lots of info about this too. I used the following
technique suggested therein. Get an ice pick and bend the tip slightly.
Remove the cover, spring, and air piston assembly
after removing the damper cap.

Refer to the Haynes carb manual to see how to
remove the metering needle. (Use a hex wrench
to loosen all the way counterclockwise, and you can
pull out the needle.) With the ice pick, _carefully_
remove the star washer at the bottom of the piston
without scratching the sides of the dashpot.
Push out the adjuster with o-ring from the bottom
of the dashpot. Replace the o-ring and reverse
the process.

Moss lists both the star washer and o-ring
as separate items.

I polished the inside of the dashpot a bit with
Simichrome to remove any scratches.
Ronald

Chris,

Replacing the o-ring so as not to lose dashpot oil should help acceleration. But I can't figure out why your car would "break down" for lack of dashpot oil. So I'm a little curious about a) how your mechanic diagnosed this and b) how putting oil in the carb got your car moving again. If your car's running again, I guess that's great but I think you must have some other kind of intermittent problem.

Derek
'79B
Derek Berger

This thread was discussed between 12/03/2003 and 13/03/2003

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