TM 5-6115-405-15
Section IV. ENGINE
6-13. General
c. Inspect and clean or replace spark plug (1) as
This section contains complete repair instruction for
required. Reset gap to 0.30 inch.
the engine parts.
Tool applications and special
d. Clean and inspect cylinder (10) for worn chrome
procedures are provided where applicable.
plating. Inspect cylinder (10), crankshaft (27), and
crankcase (29), for cracks, porous spots, and scored
6-14. Disassembly
sealing surfaces.
Figure 6-4 is a complete exploded view of the engine
e. Inspect needle bearings by trying to separate
section. In general, disassemble in the numerical
the needles at one end. If the needles can be separated
sequence indicated on figure 64; Special procedures
more than the width of one needle, replace the bearing.
and tool applications are given below:
f. Inspect loading spring (24) for damage. Check
the height and replace if less than 1/8 inch.
a. Use fabricated offset wrench to remove nuts (8,
g. Scrape heavy deposits from the top of piston
fig. 6-4 )from cylinder (10). Remove the cylinder. Pack
(20) and clean by carefully wire-brushing only the dome
rags around piston (20) to prevent damage.
area.
b. Use a 9/64-inch Allen wrench to loosen socket
head screws (13). Discard the screws. Remove both
Caution
halves of connecting rod (15) and all 31 needle rollers.
Do not clean varnish-like deposits
Slide crankshaft (27) straight out of crankcase (29).
from piston skirt or side walls of
c. Using a pair of retaining ring pliers, remove
cylinder (10). Use extreme care so as
retaining ring (17) from piston (20).
not to scratch polished chrome
d. Insert fabricated piston pin removal tool past the
surfaces.
Spiral pin in piston (20) and press or tap out piston pin
(18).
h. Using the butt end of a discarded piston ring,
carefully clean piston ring grooves in piston (20). Wash
Caution
the piston in an approved cleaning solvent.
Do not press the tool in too far or the
i. Inspect piston rings (19) for wear. Replace if
Spiral pin will shear off.
they are scored, have excessively round wear pattern,
or have machining marks obliterated.
e. Starting from the top of the piston (20), carefully
expand piston rings (19) to clear the piston, and remove
6-16. Reassembly
them.
Reassemble parts in reverse of numerical sequence
f. Using fabricated needle bearing assembling
as illustrated on figure 64. Note the following:
tool, press needle bearing (16) out of connecting rod
(15).
a. Using fabricated bearing and seal tool, install
g. Using fabricated bearing and seal tool, remove
needle bearing (23, fig. 6-4) in crankcase (29). Use the
needle bearing (23) and seal (22) from crankcase (29).
shorter shouldered end of the tool (from the interior of
Insert the longer shouldered end of the tool from inside
the crankcase), pressing against the lettered side of the
the crankcase and press the parts out in the direction
needle bearing.
shown in figure 6-4.
b. Using a new seal (22) greased to protect it from
damage, place the seal on the long end of fabricated
6-15. Inspection and Repair
seal assembling plug with the open end of the seal
a. Discard socket head screws (13, fig. 6-4), 31
facing needle bearing (23). Install the seal from the
needle rollers (14), and retaining ring (17) each time
outer surface of crankcase (29).
they are removed.
b. Discard seal (22) whenever it is removed from
crankcase (29).
6-12
