1968 Evinrude Big Twin, Big Twin Electric, Lark 40 HP Outboards Service Manual, Page 24Get this manual
Check throttle and choke shafts for excessive Check operation of choke and throttle valves to sure they correctly shut off air flow, yet move freely without bindingReplace carburetor body if valves or shafts' are excessively worn or damagedNOTE The threaded edges of the choke and throttle valve attaching screws are staked during carburetor to prevent during operationDisassembly of these valves is possible, but replacement of the carburetor body is recommendedPLUGS If necessary, remove core plug to clean out slow
Figure 3-13Needle Valve Seat Wear NEEDLE VALVES Inspect .the tapered end of the needle valves for grooves, nicks, or scratches; replace if necessarySee Figure 3-14DO NOT attempt to alter the shape of the 10wspeed needle valveCARBURETOR BODY Clean out the jets and passages, and the venturi, making sure gum or varnish deposits remainafter cleaning with compressed airclean [or final reassemblyCheck gasket surfaces for nicks, scratches, or distortionSlight irregularities corrected with the of surface plate and emery cloth