I've learned the hard way that SUs are not easily tuned if the first tune-up
steps, the valve clearances, timing, and the points gap are not adjusted
first.
Then, as far as lifting the pistons are concerned, sometimes the spring in
the dashpot wears out after a few decades, perhaps you'll want to replace
both of them.
I had a problem with mild backfiring while shifting (or any situation in
which the RPMs dropped rapidly). It turned out to be a small exhaust leak
between the manifold and the pipe, which went away after tightening the
studs.
Hope that helps. Someone's wisdom on the list was that most problems with
SUs result from timing/electrical issues.
Regards,
Charles
'74 Midget
'68 SPrite
cdsorkin@ix.netcom.com
"How about we duck inside for a Hen?"
Original Message:
_________________________
Help! My first major project with out 68 MGB-GT and I am sending out an
SOS! I tuned the carbs, following the standard directions. The major
problem is with the fuel mixture in the first Carb. I took both carbs
apart, cleaned (did not change the setting on the needle) and put them
back together, making sure both jets were at the same position. I got
them balanced out using a Unisynch, then started to work on the fuel
mixture. I started with the suggested 2 turns out, and both carbs
increased RPM when I lifted the pistons. I got to a point where the rear
carb no longer increased RMP but the front one still did. I ended up
getting the front jet all the way up, and it still increases the RPM when
I rease the piston. I took the daspot off, and sure enough, the jet is
all the way up. It was pretty late when I finished, but ran it around the
block and it seemed like I was getting some back firing when I shifted
which would imply too rich. The smoke was no longer black out the
exhaust. What did I do wrong?
The only other problem I have is that the choke no longer works. I
checked and it is not lowering the jets nor is the cam engaged by the
fast idle screw. I can pull the choke handle in the cab out, but nothing
happens. I can move the choke by hand and it is not stuck. The fitting
which holds the end of the choke cable on my carbs screws onto the back
of the first carb, but it only goes on one way and is not in the way of
the choke mechanism. Where do you find the end of the choke handle, where
it connects to the cable?
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