REMOVAL - TM-10-3930-644-14-P0205

TM 10-3930-644-14&P

The rear face of the crankcase provides an accurately

3. Clean pistons of all carbon, being particularly

machined surface for mounting the flywheel housing. A

careful to see that the ring grooves are clean

semi-circular groove in the rear face of the crankcase

and oil drain holes in oil ring groove are clean of

around the rear main bearing receives a semi-circular oil

all carbon. Inspect pistons for any cracks in

guard, and a filler block which is held in place by two

head or in piston pin bosses.

machine screws. Oil guard and filler block contain a

4. Clean oil passage in each connecting rod and

pressed-in oil seal to prevent the entrance of foreign

check each piston and rod assembly for correct

material around the main bearing.

alignment.

The camshaft extends the length of the left side of the

5. Clean valve guides and valves to remove head

crankcase and runs in three pressed-in bushings which

and stem deposits. Check fit of valves in guides

are drilled for pressure lubrication from drilled passages

and tension of valve springs.

in the crankcase.

6. Check that valve tappets are free fit in block

without perceptible side play or shake. Inspect

The three main bearing locations are machined to

for rough or grooved faces, and be sure heads

receive thin-wall precision type bearings. No shims are

of adjusting screws are smooth.

used between the case and the bearing cap. The center

main bearing is flanged on both sides to absorb

7. Check general condition of camshaft. Journals

crankshaft end thrust and to locate the crankshaft

should not be scored or burred. Cams should

lengthwise. The three main bearing caps are doweled

be smooth and free from burrs or grooving.

on both sides to provide for an accurate and rigid

8. Inspect crankcase for cracks, especially in the

alignment. The upper and lower halves of the precision

exhaust valve area.

type bearing shells are alike and are located by small

tabs with fit recesses in the case. The front and center

9. Clean the ring of carbon from around the top of

bearings have a single groove in each shell which

the cylinder bore formed above the travel of the

extends out a short distance from the oil hole and blends

top ring.

into the bearing contour. The rear bearing has two holes

10. Determine the original diameter of the cylinder

connected by an oil channel.

barrel by checking this unworn area with an inside

If the same connecting rod bearings are to be re-used,

micrometer at intervals of approximately 45.

be sure the bearing shells are kept in order with respect

to which connecting rod they go in, which is top and

which is bottom. However, re-use of bearing shells is

not recommended.

B. REMOVAL

Refer to ENGINE REMOVAL AND INSTALLATION.

Refer to relevant sections for removal/ installation

instructions.

C. INSPECTION

Important points on cleaning and inspection to be

observed are as follows:

1. Clean oil pan thoroughly. Remove oil gallery

plug and clean all passages with solvent and

compressed air.

Clean valve compartment

thoroughly. Clean crankshaft oil passages.

2. Carefully inspect the condition of the crankshaft

Figure 11-2. Measuring Original Bore Diameter Above

journals and crank pins. These surfaces must not

Ring Travel.

be scored or burred and should be checked with

a micrometer against specifications as tabulated

in TOPIC 1. FITS AND TOLERANCES

R-104-1

3-40