Figure 5-20. Cleaning Ring Grooves (Model RMP-J/1- IOG).

TM 5-4110-217-14

c. Cleaning, Inspections and Repair.

(1) Clean all parts in an approved cleaning

solvent. Dry thoroughly with clean lint-free clot Remove

carbon deposits from piston ring groove Use piston

groove cleaner tool to remove dirt grooves (fig. 5-20).

Blow out all oil passages with compressed air.

(2) Inspect piston for cracks, breaks, and

scored condition. Inspect clearances between piston pin

and piston. Piston pin is a thumb push fit. piston is

excessively loose on piston pin, install a new piston pin.

Inspect clearance between piston and cylinder wall.

Position piston In cylinder. Clearance between piston

and cylinder measured below o controlling ring, 90

degrees from pin, should 1 0.0025 to 0.0045-inch.

(3) Inspect the piston for fractures at the ring

lands, skirts and pin bosses. Check for wear at the ring

land using new rings and a feeler gauge shown in figure

Figure 5-21. Inspecting Ring Lands (Model RMP-J/1-

5-21.

IOG)

(4) Check for excessive ring side clearance (

improper width rings. These can result in ring breakage.

New rings in worn ring grooves will n have good cylinder

wall contact (fig. 5-22).

(5) Check for pistons showing signs of be

scoring or burring, excessive skirt clearance, wax or

worn ring lands, fracture or damage from detonation.

Replace piston pins showing fracture scored bores, or

bores out of round more than 0.002-inch.

(6) Use a new piston pin to check the p

bushing in the connecting rod for wear. Clearance piston

pin In rod should be 0.0001 to 0.0006.

d. Reassembly.

(1) Before installing new rings on the piston

check the ring gap by placing each ring squarely in

Figure 5-22. New Ring Worn Piston Ring Groove (Model

RMP-J/1 -IOG)

its cylinder at a position corresponding to the bottom of

its travel (see fig. 5-23). The piston ring gap in cylinder

should be 0.010 min. to 0.023 max. Rings which are

slightly oversize may be filed as necessary to obtain the

correct gap, but do not use rings which require too much

filing. Standard size rings may be used on .005-inch

oversize pistons. Other oversize rings must be used with

corresponding oversize pistons. Rings of the tapered

type are usually marked top on one side, or identified in

some other manner and the ring must be installed with

this mark toward the closed end of the piston.

(2) Drive piston pin bushing(205) m connecting

Figure 5-20. Cleaning Ring Grooves (Model RMP-J/1-

rod (197).

IOG).

(3) Position piston (206) on connecting rod

(197). Thumb-push piston pin (204) through piston and

connecting rod. Secure pin with two retaining rings

(203).

Change 3 5-13