By the end of the 1978 model year, Kawasaki had received a lot of complaints about driveability of their motorcycles, especially the KZ1000 models. Kawasaki had been forced to use jets that caused the carburetors on their bikes to operate very lean due to the onset of EPA regulation.
As a result, in 1979, Kawasaki began using accelerator pumps on the KZ1000 model line up and later the KZ650s followed suit. These accelerator pumps add ONE SQUIRT of fuel when the throttle is opened and the lean jetting problem was eased by the addition of this fuel and st off-idle lean bogging went away. The accelerator pump doesn't add horsepower or effect much except off idle.
VM28SS With Acellerator Pump
The VM28SS assembly above has an accelerator pump. The pump can be recognized by use of an oversized #2 carb bowl. The lever which points to the center of the assembly and joined to the throttle butterfly mechanism by a rod is what operates the pump. The lever inserts into a cover which houses a spring loaded rubber diaphragm.
This mechanism is used to squirt gas up into the carb throat (venturi) through the small brass nozzles that can also be observed in each carb throat. Carburetor assemblies with this style accelerator pump will also have small diameter hoses linking the other three carburetor bowls adjacent to the number two carburetor which carry additional fuel from the pump to their nozzles.
VM Series Carburetor Assmebly With NO Accelerator Pump
The assembly above is a VM29 smoothbore type. It has no accelerator pump as jetting was adequate so that no lean condition, off idle exists. Other carburetor assemblies that also did not require accelerator include those on 1977-79 KZ650 models as well as all Z1, Z1A and Z1B, all KZ900 and KZ1000 models through the 1978 model year. No Suzuki models using VM series carburetors ever used accelerator pumps. Note all bowls are the same and there are no fuel hoses joining them.
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