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Engine Adjustments


The throttle control cable is actually an assembly of three cables: the throttle grip cable, the carburetor cable, and the oil pump cable. The throttle grip cable runs from the throttle grip to the cable assembly junction where it connects to the carburetor cable, which leads to the carburetor, and the oil pump cable, which leads to the oil pump.

Since the throttle grip controls both the carburetor and the oil pump simultaneously, it is important that each cable be adjusted to its designated base position so that the quantity of oil and fuel/air mixture reaches the engine in the correct proportion at all throttle openings. Stretching of the cables creates excess play at the throttle grip and alters the base positions of the cables at the carburetor and the oil pump, necessitating periodic adjustment.


The throttle grip cable, connecting to both the carburetor cable and the oil pump cable, controls both the carburetor throttle valve and the oil pump lever. If there is too much play in the cable, neither the carburetor nor the oil pump will respond immediately when the grip is turned. Most of this excess play must be adjusted out. However, a small amount has to be left so that the steering movement will have no effect on the throttle valve or oil pump lever.


Loosen the lock nut at the throttle grip end of the throttle grip cable.

Turn the adjusting nut until the desired amount of throttle grip play is reached.


Tighten the lock nut.


The carburetor cable forms one of the two lower branches of the throttle control cable assembly. It is adjusted so that if the throttle valve were to be closed fully (not at idle but all the way down), all the play in the carburetor cable would be taken up.

The play that develops as the cable stretches will cause a delayed engine response, and should faulty adjustment cause the cable to pull the throttle valve out of its rest position, proper idling cannot be achieved. If the carburetor cable is out of adjustment, the oil and fuel/air mixture ratio will be incorrect, resulting in over or underlubrication. Adjust the carburetor cable whenever the throttle does not respond properly and at least every 3,000 km (2,000 mi.) to compensate for cable stretch.


Warm up the engine for about 5 minutes, and then turn off the engine.

Check to see that the throttle grip has the proper amount of play.

Turn out the idling screw (throttle stop screw) until the throttle valve reaches its lowest position.

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