Z Tech Tips Triple Mikuni Carbs
Tony D Triple Mikuni Set Up Procedure
the downlinks to each of the carburettors so the carburettor throttle bell
cranks are resting against their IDLE stop screws. This is a greyish screw
attached to a stamped sheet metal bracket on the right or the left side of EACH
FOR BENT THROTTLE SHAFTS. Put you meter on the front and the rear barrel of EACH
carburettor. Find which one is the lowest reading, that is the one you need to
do synch on
A BARREL on each carburettor. FRONT OR BACK. Doesn't matter which, do this with
regard to the above test, so you have the throttles that are CLOSED THE MOST at
idle. Usually this is cylinder 2, 4, 6 on the standard setup.
the synch meter so the HIGHEST READING barrel of those three is in the middle of
the meter's range by adjusting the screw (Unisynch) or by reading the number
(Weber Tool). By using the above mentioned IDLE STOP SCREW, make each barrel
flow the same by adjusting the screw in or out. Engine speed is irrelevant at
they are all in synch, then slowly turn each one back down or up to make idle
speed (850-900rpms). Check on the same three barrels each time so you have them
all flowing EQUALLY at that idle speed.
the brass screws using a tachometer or mercury manometer for highest idle speed
(Best Rich setting is preferred for performance, search the archives, I'm not
going over that again)
the idle speed with the IDLE STOP SCREWS again, and make sure they are flowing
as necessary until you have the highest idle vacuum and lowest throttle opening.
You now have carburettors synched at idle, and adjusted for idle. Now to adjust
the car off, no sense doing this and having it vibrate and be hot while your
fingers are in there. Adjust EACH linkage, one at a time so they EACH attach to
the bell crank on the throttle rod easily---they slip on and off the little
pivot ball WITHOUT moving the other linkages. If you have one too short, that
carburettor will be at idle speed and the others will be held open slightly at
idle, and this will continues up the speed range. Once all the linkages are
adjusted so they are opening evenly, and all slip on and off without disturbing
any of the other carburettors, depress the throttle and make sure they all open
the carburettors to 100% open, and at the same time. It is possible if one of
the bell cranks on the throttle rod is far enough out to line with the others
you could have one carb not opening all the way, but this is not usually the
Restart the car, check your idle synch--it should not have moved.
If it did, disconnect the throttle linkages, and see which one is too short
holding the other two open and fix it. Once they are confirmed to be in idle
synch, then open your throttles off-idle, and USING THE SAME BARRELS OF 2,4,6
and opening your uni-synch almost wide open, stick it over the barrels and see
if they are all flowing the same off-idle. If so, you are done. The uni-synch
SUCKS for this part of the test, and really for the first part of the test. I
prefer the Weber tool with a direct reading number, but such is life.
You are now done. Use locktite green on all the linkages to lock them in place, and LEAVE THEM ALONE. This should NOT have to be anything done once done correctly and properly secured the first time.
Bent throttle shafts suck, and I don't recommend "bending them back" like Brian said, because I have never had one go back and not go too far. There was a time you could buy new shafts, but good luck with that now. If you synch them this way (by using the furthest closed barrel) you should be fine even with shafts that are slightly tweaked.
More Tony Tips:
It sounds difficult, but is pretty easy. If you had the carbs off the manifold, you can get REALLY close using a 0.002" feeler gauge and presetting all the idle stop screws that way, and then adjusting your linkages to match up as above---doing it that way really saves time, because in theory they will all be flowing the same with the same throttle opening unless you have a problem with an individual cylinder
Do a valve adjustment, general tune up and new plugs to make sure everything is up to snuff and they are all hitting strongly as they should before screwing with the carbs.
The above process is the same for triples, quads, duals. Same for VW, Porsche, BMW, Toyota, Nissan.....
Carbs is carbs... Piece 'o Cake.