PROJECTS IN FARM MACHINERY REPAIR 327 



16) Disconnect pipe line from carburetor to fuel tank. See 

 that it is not clogged. 



17) Remove carburetor or mixing valve and examine the fol- 

 lowing points: (a) Type of air valve, if any; (6) how the 

 gas is drawn to carburetor; (c) how it is controlled at the 

 carburetor; (d) screw out the needle valve and note its 

 condition. 



18) Clean out any dirt or other material that may be col- 

 lected in the cooling system. 



19) Reassemble the engine in the reverse order in which it 

 was dismantled. 



20) Adjust the engine by timing the valves and the ignition 

 and setting the governor for rated speed. 



General Questions to Answer in Report on this Exercise: 



1) Does the engine have high- or low-tension ignition? 



2) Draw a diagram of the wiring. 



3) Why is insulation provided on the wire? 



4) Is the fixed or the movable electrode insulated on the 

 igniter block? Why? 



5) If a spark plug is used, draw a sketch showing its con- 

 struction. 



6) How far apart are the spark plug points? 



7) Why are the points on the spark plug separated and 

 those on the igniter block brought together? 



8) Why is it necessary to clean the motor cylinder occa- 

 sionally? 



9) Why grind the valves? 



10) What causes carbon to collect in the cylinder? 



11) How is the carbon best removed? 



12) What happens if a piston ring is broken or stuck? 



