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carb tuning/synchronizing- HELP !!

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14 Feb 2006 20:44 #23961 by oldkaw
carb tuning/synchronizing- HELP !! was created by oldkaw
I finally broke down and bought a synchronizing kit. Unfortunately no instructions were included. I have 4 dial gauges with restricters that I figured out how to use to keep the needles from bouncing around like crazy. Anyway is there an ideal measurement that your vacuum should be at ? I've been told it doesn't matter as long as the difference isnt more than 2cm/hg between all the carbs. Anyway, by playing around with my adjustment screw on each carb I could get the readings to move to anywhere on the dial.
Also, can someone point me in the right direction for step by step instructions ?
Here is what I've done : Warmed up the engine and set the idle at around 1000rpm according to the stock tach. The bike is tuned up and has a clean air filter installed. The gauge tubing is on each carb and I've opened the restricters and let the needles bounce. Then I closed the restricters and got my readings.
I dont know if what I've done is right or wrong or if I've missed any important steps. By the way, these carbs are keihin cv34's on a zn700.
Any help would be appreciated. Thanks in advance !

2 1984 zn1100, 1 1985 projects
1984 zn700 oil cooler, kerker 4-1, mikuni 34's, k&n pods
1984 zn700 stock
1982 kz750m1 stock
1975 cb550k
1975 cb360t

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14 Feb 2006 21:38 #23973 by GargantuChet
Replied by GargantuChet on topic carb tuning/synchronizing- HELP !!
It sounds like you've hit it, but just to be complete, here's Clymer's 11-step program towards more harmonious carb operation:

Before starting, check your timing, valve clearance, and idle speed.

1) Put the bike on the centerstand, start it up, and let it reach normal operating temp.

2) Shut it back off. Pull the rubber caps from the intake manifolds.

3) Connect the gauges.

4) Start the engine. The normal reading should be 18-24 cmHg. The difference between any 2 cylinders should be less than 2 cmHg. If the difference is greater, proceed as follows.

5) Shut off the engine.

6) Remove the fuel tank. Unless you like fire hazards, don't rig up a temporary supply, just run with what's in the bowls.

7) Remove the top covers from the carbs and loosen the locknuts.

8) Start the engine and let it run at idle.

9) Fiddle with the screws until all carbs are within 2 cmHg of each other. Backing out the screw decreases vacuum, turning it in increases vacuum.

10) If, after completing this procedure, any carburetor reads less than 14 cmHg, this indicates trouble within the carburetor. Take it apart and clean it.

11) Remove the test gauges, reinstall the four manifold vacuum caps, and reinstall the gas tank.

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