PAT asked about his Zenith-Stromberg carb losing oil and what to do about
it. The draught under the piston draws the oil from the dashpot and burns
it up in combustion. Replace the O ring in the following manner: Remove
the top and the carb and the spring; Remove the piston with diaphragm;
Remove the diaphragm; use a 1/8" allen wrench (half of the adjusting tool);
to UNSCREW the adjuster screw perhaps five turns; remove the set screw from
the side of the piston; Withdraw the needle (BE CAREFUL NOT TO DAMAGE IT);
and NOW you can withdraw the adjuster screw -- here's how. I use a piece
of brake line about one foot long and my brass hammer. Oil up the dashpot
(full), and turn it upside down on a cloth. Place the brake line (or any
suitable LONG punch) on the brass adjuster screw and within four or five
taps, drive the adjuster screw onto the rag. The brass adjuster screw is
held in place with an IRREPLACEABLE star washer -- so don't lose it!
Replace the O ring (#010 standard neoprene O ring). GREASE up the adjuster
screw, and the dashpot. Place the O ring, topped by that star washer and
PUSH the adjuster screw and star washer back down the dashpot until it
stops. Fit the needle (you'll have to push hard to force the grease out of
the hole), fit the needle grub screw nearly tight, and turn the adjuster
screw CLOCKWISE with your 1/8" allen wrench until the needle is TIGHT.
Tighten the grub screw all the way, then use your brake line and tap the
star washer DOWN so it fits snugly against the bottom of the dashpot -
watch out for the needle! Fit a new diaphragm. You MUST adjust the carb
when done. Adjust it just like an SU -- lift the piston to judge the
change in rpm. As you slowly lift the piston, the rpm should increase
about 50. If the engine stumbles and drops off the mixture is too lean;
and conversely, if the engine runs faster, faster, faster as you lift the
needle the mixture is too rich. Clockwise is rich; anticlockwise is lean.
Adjust the car so it runs well - not so that it pollutes correctly. The
needles are good only for about 30,000 miles. MGBs use 45H. Any other
questions? Fast Forward! John Twist
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