Roadsterites,
Having done this more times than I'd like to count on 2 my old 510's with
40mm Mikunis and my current triple 40mm Mikuni setup on my 240Z...
First, make sure you're valves are adjusted properly. If you're intakes
are all different, you can't make accurate adjustments with the carbs. The
intakes will all be drawing at different rates.
It's a good thing to pull the linkage if you're unsure if it was set right
to begin with. Pull them and make sure they are the exact same length.
After that you don't really need to reset the linkage arm lengths, they
really don't move around a lot. The thing that loosens up and moves is the
bracket arm to the linkage shaft. There's only a single tightening screw
which clamps it down to the shaft. Make sure you don't have any play within
the shaft bushing also, it makes a difference.
Kind of a no brainer, but I've had this happen to me once...make sure all
your jets are tightened down securely. The jets are underneath the top
plate.
Back off the idle set screws until the plate bottoms out without touching
the screws. Tighten up the bracket arm to linkage shaft screws with the idle
plate bottomed out. Then slowly turn the idle adjustment screws in until
they JUST barely touch the plate. Do this for both carbs. I usually start
out with screwing them both in 1 1/2 turns equally to get the car idling.
Screw in the mixture screws until they bottom out, but be VERY careful,
don't crank down on them or you'll bend the needle points. Once they're both
down, back them off 2 1/2 turns to start. Fire it up. Mikuni (Solexes)
usually like about 4 1/2-5 psi fuel pressure. Pull the air cleaners, but
leave the stacks on. Take your measurements, they should all be equal
intakes. Mine read 5-5 1/2 psi intake. Do gross adjustments with the idle
set screws. (ie. if 1/2 are reading 4psi and 3/4 are reading 6psi, adjust
the idle set screw on 1/2) Do micro adjustments with the mixture screws. I
try to never have more than 1/2 turn difference between any/all of the
mixture screws. The Synchrometers (little red bead in a tube) are tough
because once you put it over the stack it kills the engine, take your
measurement quickly to get an accurate read. You can open up the amount of
air the Synchrometer lets in if you can't get a good read. I have a dial
type synchronizing tool ($40 from Top End Performance), much easier to use
because it doesn't affect engine idle and is very sensitive (you can see the
dial move as you make adjustments).
To fine tune with your current main/pilot jets, get it idling around 1K
rpm. Take the car out for a spin and slam on it from a dead stop. You have
to play with the mixture until you minimize the amount of bogging off the
line (open up each screw equally in increments of 1/4 turns). BUT, keep in
mind Mikunis and Solexes are racing carbs meant for high rpm running.
Depending on your jetting, you can minimize this condition but will lose out
on the top end. It's all a balancing act and depends on what conditions you
are going to be driving your car in.
I hope this helps!
Good luck!
Stan Wada
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