I have a Midget which used to have probably the exact same ZS carb
as your Spit as it also had the Spit 1500 motor. I rebuild the carb and
had no problems, it ran fine after I rebuilt it. Eratic idle can be alot
of things eg. a vaccum leak somewhere, aften around the throttle shaft
bushings. You can test where the leak is (if you have one) by spraying
carb cleaner at the spot and see if the engine revs/tone changes. Next you
might have a torn diaphram, easy to check, just undo the 4 screws holding
the dashpot on, carefully lift it out and inspect the diaphram. Next the
needle might be scored. It is spring loaded so it scrapes along the jet sides
all the time, feel the needle and inspect it for a flat side or spot.
There are two funky valves on the carb, one has a rubber diaphram with a metal
plug in its center, sometines this rubber gets brittle and does not alow the
plug to do its job. Do not touch the other valve, I didn't as I think its
a no touch deal.
There is not too much else you can do with the thing still on the car.
Oh, get rid of the auto choke, they are useless. I replaced mine with a $7 man
ual conversion kit for the local auto store. Then you have control!!
Chances are that you will have broken the diaphram unless you used the
proper tool to turn the screw as the screw becomes stuck. If the dashpot oil
leaks, ie you must top it off too often then you must replace the small
rubber O ring deep down where the mixture adjust screw sits.
I have the ZS from my midget in a box as I put a SK sidedraught on it
(an SK IS better then the weber BTW). If it would help, I can send you it
just to bolt it on whilst you toy with your one, then you can send it back
when you are done. Although of course you would still have to adjust it.
If you have any specifics to ask, just ask. I also have a set of SUs
with manifold for the Spit (thats twin SUs!!) from UK so fuel emission
rubbish. But these are very much dismantled.
Cheers Dennis
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