Mike,
We have similar emission requirements here in NJ. How are you raising
the piston? I believe the preferred method is using a small diameter
long screw driver to gently push up on the bottom of the piston while it
is running (seems clumsy to me). You will have to have the air cleaner
off to do this. There are excellent directions for tuning the ZS carb
in the Moss catalog. The biggest problem is the possibility the ZS's
automatic choke is not working (more on that later).
Anyway, I discovered two things with my 1978 MGB. First, the catalytic
converter was "toast". The cat's service interval is 25,000 miles and
(at 54,000 miles) the inside of mine was all broken up and mostly
missing. I suppose the PO could have done it, but it looked more like
it had melted and broken up on it's own. No matter - I replaced it
(Moss 444-175, about $190). Second, the air rail and inlets to the head
typically clog with carbon. Mine were completely clogged! Take the
air-rail off (carefully - mine broke in the process) you can use a small
drill bit held in your fingers to remove the carbon. Make sure the air
rail is clear by blowing through it and checking each orifice. I used
the same small drill bit and a vacuum cleaner to clear out the holes in
the head. I also used a wound guitar string to check that the holes
were clear all the way into the exhaust ports. The air pump is
necessary to add O2 to the exhaust gasses so the Catalytic converter can
do it's work.
You also need the special tool sold to adjust the needle height (Moss
386-310, about $9). Anti-clockwise to lean-out the mixture and
clockwise to enrich. I also broke down and bought the Gunson digital
emissions meter. It's expensive (Moss 386-210, about $200), but I doubt
I could have gotten it adjusted correctly without it. The new cat and
working air pump got my CO down to about 2% and when I went to emissions
inspection it registered at 0% on their equipment! You also need to
check the plastic (nylon?) air regulator assembly on the side of the
carb is adjusted correctly. (Mine was completely missing when I bought
the car.)
More regarding the automatic choke: When this malfunctions the carb
will run REALLY rich and, assuming your air pump and catalytic converter
are working, will make the catalytic converter glow cherry red! (I
actually had this happen!!!). Can you say "FIRE HAZARD"? Apparently
common with ZS equipped car owners. The ZS choke assembly is available
as a separate unit for about $200, but I ended up replacing the whole ZS
carb with one of those SU HIF44 carb units (about $500). It's much
simpler (one screw for the mixture) and a manual choke. I'm still
tuning it, but the chance of an engine fire seems greatly reduced.
Hope some of this helps,
donny v
1978 MGB
>>> "Michael W. Jose" <michaelwjose@hotmail.com> 5/12/2004 2:19:42 AM
>>>
Gang,
I've been trying to tune my lousy ZS for emissions, but I keep running
into
one problem. If I pull up on the damper, the plunger falls off the
bottom and
I can't move the piston up and down to see how I'm doing on tuning.
>From what
I understand, checking the mixture by opening the piston is a good way
to
tune, but I can't keep ahold of the piston to do this, once I've, say,
topped
up the oil in the carb.
Anyone have any experience on a good way of doing this?
One of these years I'll get good at tuning this stupid thing...
Car is a '79 B, cat, air pump, egr, choke valve all required, and the
car is
tested for and failing both HC and CO.
TIA
Mike Jose
79 B
Chandler AZ
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