In preparation for the required California SMOG check, I have been
troubleshooting the rough running of my new project, a '79 MGB. By
Disconnecting, plugging or blocking off, I have eliminated the gulp
valve, the EGR valve, and the brake servo as problems. The stock
manifold has been installed with a new gasket. With all the above
temporally removed from the system, I have achieved a low idle speed
with an occasional stutter. When I try to increase the speed of the
engine it will increase to about 2000 RPM and then bog down to about
1500 Rs and sound horrible. No amount of needle adjustment helped.
Believing the carb to be excessively rich, I replaced the water jacket
choke housing gasket with a solid one to block it off. The problem
remains. Now here is the curious part that I need the MG list's
collective wisdom to ponder. If while opening the throttle I Hold the
piston with my finger so that it only goes up part way, the engine will
rev freely to 3000 or above !!! Please help, Does holding the piston
keep the needle from withdrawing and thus leaning the mixture? or does
holding the piston cause a choking action that enrichens the mixture? I
am tending to believe that maybe the needle jet is worn out, or the
piston spring is too soft. The spring would be easy to replace but can
the needle jet be replaced? It looks like it would require a special
tool. At any rate the needle jet does not appear to be available from
MOSS or VB. I put it to the list
Thanks
Eugene
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