The fuel ratio control is on the fuel system as a limit for the amount of fuel for injection during an increase in engine speed (acceleration). The purpose is to keep the amount of smoke in the exhaust gas at a minimum.
FUEL RATIO CONTROL
1. Chamber. 2. Spring. 3. Spring. 4. Bolt.
When the engine is running, air pressure from the inlet manifold is in chamber (1) of the control. The combination of the force from the air pressure and spring (2) makes a balance with spring (3). The balance controls the position of bolt (4). When the governor control is moved to make an increase in engine speed, the linkage moves to turn the fuel control shaft to put more fuel into each injection.
When the adjustment of the fuel ratio control is correct there will be enough increase in the fuel for injection to make the engine accelerate rapidly. If the adjustment is correct, there will not be too much smoke in the exhaust when the engine accelerates.
FUEL RATIO CONTROL
4. Bolt. 5. Lever. 6. Pin.