ENGINE. - TM-10-3930-622-140123

6-74.

ENGINE.

(using adapter if necessary) (figure 6-28) and crank

engine for at least four compression strokes. Note

a. General. The engine is a six-cylinder, L-head,

reading on first full stroke as well as on final stroke. (See

water cooled unit of generally conventional design.

test indications (2) below.)

Overhaul can be

accomplished with tools and

equipment ordinarily available at the overhaul facility.

NOTE

Detailed instruction for complete overhaul is given;

however, if preliminary diagnosis has shown a specific

defect to -be corrected, do not disassemble the engine

All cylinders must be tested the same

further than necessary to restore the engine to normal

number of compression strokes to

operating condition. The instructions in this manual

assure accurate readings. Slightly

emphasize that which is unique or special in repairing

higher compression readings will be

this particular engine. In all cases follow good general

obtained if throttle and choke are

shop practice in performance of these instructions.

opened during test.

Certain specialized shop equipment will be required to

perform a complete overhaul, such as a crankshaft

(d) Refer to manufacturer's specifications for proper

grinder and a boring bar. Detailed instructions for

cranking compression pressure.

operation of such equipment is not within the scope of

this manual. Refer to the publication covering the

(e) If readings are below normal or uneven, place a

equipment being used for this information.

small quantity of OE 30 oil on top of each piston through

spark plug hole and retest compression.

b. Engine test.

(2) Test indications.

(1) Test compression as follows:

(a) Normal. Compression builds up quickly and

(a) With engine warmed up, remove plug cables

evenly to specified compression on each cylinder, varies

from spark plugs, loosen plugs 1/2 to one turn, reinstall

less than 10 pounds between highest and lowest reading

cables and start and run engine for at least thirty

cylinders.

seconds, to get rid of carbon loosened by plug loosening.

(b) Ring trouble. Compression low on first stroke,

(b) Turn ignition switch OFF (or ground coil high

tends to build up on following strokes but does not reach

tension lead) and remove all spark plugs.

Put

normal. Improves considerably with addition of oil.

transmission in NEUTRAL.

Figure 6-28. Compression Test