Examine magneto ground leads to
determine that RIGHT switch position fires front plugs and
LEFT switch position fires rear plugs. Make this
examination prior to changing spark plugs, making
ignition harness test on cylinders which are operating, or
are operating intermittently. In addition, examine ignition
position, the difficulty may be due to
incorrect valve clearances, impeller oil
seal leaks, leaking intake pipes, or lack
of compression (blowby).
Repeat cold cylinder check for
necessary. Additional cold cylinder checks will be
conducted at different speeds in event any roughness Is
still encountered during ignition system check
Cooling of the engine between checks
is not necessary as airflow created by
incoming fuel-air mixture into cylinder
will be sufficient to cool any cylinders
which are functioning on one check
and fail to function on the following
Chalk test. The chalk test should be
used when the cold cylinder tester is not available. Test
using the following procedures.
Mark each cylinder with a piece of
white marking chalk, A-A-320.
paragraph (e) above.
Examine each mark after engine
shutdown. Cylinders having marks unchanged In color
are dead or operating intermittently. The marks for a
normal operating cylinder will change to a pink color.
Cylinder repair. Cylinder repair can
be accomplished by using the following procedures as
Repair cracked, nicked, or broken
cooling fins by profiling damaged area using a file to
smoothly round all edges. Corners shall have at least a
1/4-inch radius and removed area nut shall not exceed
one percent of the total fin area.
Magnetic or dye-penetrant inspect fins
that are profiled to outside of dome to
ensure that crack does not extend into
Repair broken or loose studs in
tapped hole by using helical inserts.
When more than two adjacent nuts are
known to have been loose during
engine operation, or when more than
cylinder will be replaced and all studs
Place cover on a surface plate and,
using a feeler gauge, measure clearance between surface
plate and rocker box cover mounting surface. Refer to
the applicable maintenance manual for allowable limits.
Accomplish procedures 4, 5, and 6
when surface does not meet specified
Place a small amount of valve
grinding compound, A-A-1203, on a lapping plate.
In the event no grinding compound is
available, a fine abrasive cloth, Federal
Specification P-C-451, may be used.