Attention! Synchronizing the carburetors of an inline four-cylinder engine is a very important and complex operation. It is not recommended to conduct it if you are not confident in your abilities. In this case, it is better to contact specialists. For synchronization, a special device is required - a vacuum gauge, which is 2-6 precision pressure gauges necessary to measure the vacuum in the intake tract of each engine cylinder.
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Vacuum gauge with four pressure gauges for synchronizing carburetors
Seat must be removed to synchronize carburetors (see «Seat - removal and installation») and fuel tank (see «Fuel tank - removal and installation»). Instead of a fuel tank, it is necessary to install a separate container with fuel located above the carburetors, which will feed the motorcycle engine and at the same time not interfere with adjustments. Connect an additional container of fuel to the fuel hose running from the fuel tap to the carburetors.
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Warm up the engine to normal operating temperature, then place the motorcycle on the center stand.
1. Turn off the engine and unscrew the three adjusting screws of carburetors 2, 3 and 4 (carburetors, like cylinders, are counted from left to right in the direction of travel). Consistently connect the fittings of the pressure gauges of the vacuum gauge to the inlet channels of the cylinders. The vacuum gauge fittings are connected to the openings of the inlet channels of the third and fourth cylinders (marked with arrows).
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2. Disconnect the vacuum hose from the fuel cock and connect it to the first pressure gauge of the vacuum gauge, and connect the fitting of the second pressure gauge of the vacuum gauge to the second cylinder (marked with arrows).
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3. We start the engine, warmed up to operating temperature and set the idle speed screw to the crankshaft speed of 1200±100 min-1 (see «Idle system - speed control»).
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3. Rotating screws «quantities» on carburetors, we achieve uniform vacuum in the intake tracts of all cylinders. Synchronization is performed on the carburetor of the second cylinder.
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4. Check the vacuum at operating speed (4000-6000 min-1), by turning the throttle control knob. The engine should quickly gain and lose speed. After this procedure, the synchronization of carburetors can be considered complete.
We unscrew all the fittings of the vacuum gauge and plug the holes in the intake tract with standard screws, after which we connect the vacuum and fuel hoses to the tap and install the fuel tank and seat in place.