Section V. CONNECTING ROD PISTONS AND RINGS

TM 5-4110-217-14

g. Check the rotators periodically by removing the

smaller diameter of the tapered valve guides must face

toward the valve head. Install 0-ring (173) on intake

cylinder heads and cranking the engine.

When

valve side only.

functioning properly, the valve is rotated a fraction of a

c. Install valves (177) & (178) through aligned holes

turn each time it opens. If rotators are faulty, install new

of valve guides from which removed.

ones.

d. Install valve spring (172) and valve rotator (170)

5-20. Installation.

& (171). Depress springs with valve spring compressor,

NOTE

Onan Part No. 420-0119, and lock spring in place with

Refer to paragraph 1-5 for dimensions

valve spring washer lock (169).

and clearances prior to valve installation.

e. Install valve tappet cover (157) using four bolts

(158) and washers (159).

If replaced, install tappets (168) in valve

f. Install cylinder head (para. 5-15c).

chamber from which removed.

b. If replaced, install valve guides (174) in valve

ports of crankcase from which removed. The

Section V. CONNECTING ROD PISTONS AND RINGS

5-21. General.

The engine is a two cylinder engine equipped with

two connecting rods, two pistons, and two sets of rings.

The connecting rod is aluminum and comes equipped

with bushings and place bolts. The piston comes with a

piston pin and pin retainer. The ring set is made up of

two compression rings, one oil control ring with an

expander.

5-22. Connecting Rod, Piston, and Piston Rings.

a. Removal (fig. 3-11).

CAUTION

Whenever there is a noticeable wear ridge

at the top of each cylinder, remove the

ridge with a ridge reamer before removing

the pistons. If the ridge is not removed,

the rings can catch the ridge when the

pistons are pushed out and cause a ring

land fracture (fig. 5-19).

(1) Remove engine accessories and other

Figure 5-19. Wear Ridge on Cylinder Wall (Model RMP-

major assemblies and components described in

J/l-10G)

paragraph 5-1 thru 5-20.

(2) To remove the piston and connecting rod

assemblies, turn the crankshaft until a piston is at the

NOTE

bottom of the stroke. Bend out tabs on lockwasher (195)

Keep the connecting rod bearing caps

to release screw (196). Remove the screw (196) and

and bearings with their respective rods

washer (195) from the connecting rod. Lift out the rod

Tag each piece.

bearing cap (197) from the rod. With the end of a

hammer, push the rod and piston assembly out of the

b. Disassembly.

cylinder.

(1) Using a piston ring spreader tool, remove

CAUTION

piston ring set (207) from piston (206).

Be careful not to scratch the crackpin or

(2) Remove retainer ring (203) from piston pin

the cylinder wall when removing the

(204) in piston (206). Push out piston pin. Separate

parts.

piston from connecting rod (197). Drive piston pin

bushing (205) from connecting rod (197).

Change 3 5-12