175 Cd Carb Manual
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To start viewing messages, select the forum that you want to visit from the selection below. If you enjoy BCF and find it useful Please Consider Why Subscribe? Not all ZS carbs are adjustable though - some have a fixed needle and you need to swap the needle to adjust the mixture.
You might want to check this before ordering the adjustment tool. Perhaps the easiest way is to pop the top cover off (4 screws) and lift out the spring/damper/diaphram (sounds like you may have already done this) and use a regular allen key of the correct size down in to the piston/damper shaft to adjust the needle up and down. A note of caution - if the carb is of the adjustable type, and you adjust the needle to far lean (i.e. Down out of the damper body) it will disengage from the adjusting screw, and you cannot adjust it back up.
If this happens, just gently push the needle back while turning the adjusting screw clockwise (rich). I've found a good starting point is to have the shilder of the needle flush with the body (this is about 1-turn down from max. Rich, and about half the two-turns of full adjustment on these carbs) Also check the diaphram for tears and make sure the damper moves freely when reassembled etc.
Although not intended to be adjustable, the jet will move if you put enough force on it. IMO it shouldn't be necessary though, unless there is something else wrong. I once fought overheating problems on a TR3A for a long time that eventually turned out to be worn jets. Had SU carbs so not the same as your ZS; but similar. With both carbs, the mixture adjustment actually affects the entire range.
So, if some other factor is making it idle rich; and you lean out the jet/needle to correct the idle; the cruise mixture will now be too lean and potentially cause problems. On my Dad's TR3A, it cost him an engine rebuild when the lean mixture finally eroded a valve stem enough to break.
Stromberg carburettor The Stromberg carburettor does not have a regular service schedule, but should be cleaned about once a year. Replace worn parts as necessary. Dirt which has penetrated the fuel filter, and residues from chemicals in petrol build up inside. Needles and jets wear out after a few years' use. The rubber diaphragm may become holed - and even a tiny hole causes loss of power.
As the hole enlarges, the engine will eventually do no more than idle. Remove the carburettor from the car to clean it. Keep it upright to avoid spilling petrol, then empty it safely.
Clean all parts except the diaphragm by rinsing in a dish of petrol. Removing the dashpot and piston.
Loosen the grub screw to free the needle. A badly worn jet needle has a groove round it, but less severe wear is invisible.
Zenith Stromberg 175 Cd Carb Parts
Wear does, however, affect performance, so replace the needle every few years. There are many needle sizes: be sure to get exactly the right one. Remove the needle by loosening the grub screw in the side of the piston. To remove the diaphragm carefully undo the screws of its retaining ring.
Lift off the retaining ring and diaphragm. Hold the diaphragm up to the light and check it minutely for the tiniest hole. This type has to be levered off with a screwdriver - take care not to scratch the carburettor body. Older models have a pin that you can usually remove with your fingers.
If it is stiff, gently prise it out sideways with a thin screwdriver. Emission-control models have a pin set in clips: lever it out carefully with a screwdriver. The float needle valve is screwed into the base of the float chamber.
It is in one piece and cannot be dismantled for cleaning. If it is worn it must be replaced. If the float needle valve is blocked you may have to replace it.
Adjusting the float. With the holder removed, pull out the jet. Lift off the jet holder and pull out the jet. Wash the jet in clean petrol and blow through it with a foot pump to clear it. Check the rubber '0' ring round the jet holder for signs of wear or cracking. A failed ring will allow petrol to leak from the float chamber.
Lever off the ring with a pin or thin screwdriver; take care not to scratch the surface. Roll the new ring on over the holder. After reassembling the carburettor, centralise the jet (See ) if necessary.