Figure 4-20. Adjusting Tappets

TM 55-4920-335-14

with that of the crankshaft. Install camshaft in crankcase. Be

sure spring and plunger are in place in end of camshaft to hold

it in position endwise. Insert tappets in proper position in

crankcase. Clean all dirt and other deposits from fins of

cylinder blocks and install them on same side of engine from

which they were removed. Tighten mounting nuts 62 to 78 foot

pounds torque.

(2) Position crankshaft in crankcase and install main

bearing plate. Use additional shims on main bearing plate if

necessary to obtain crankshaft end play of 0.002 to 0.004 inch

when engine is cold. Timing marks on crankshaft gear and

camshaft gear must match up (figure 4-10) otherwise engine

will not operate properly if timing will be off and engine will not

run. The word TOP is cast on outside of main bearing plate

and must be mounted accordingly. Mounting main bearing

plate upside down would prevent proper lubrication. Tighten

main bearing cap screws 25 to 30 foot pounds torque.

(3) Install valve assembly (figure 4-16). Be sure to

assemble roto-caps on end of valve stems. Adjust tappets

(figure 4-20). With tappets in lowest positions, engine cold, the

clearance should be: Inlet Valves 0.008 inch: Exhaust Valves

0.016 inch. Install valve tappet inspection plate.

Figure 4-21. Installing Piston Rings

(4) Install piston rings by placing open end of ring on

piston first as shown in figure 4-21, spreading ring only far

(5) Place bearing shells in proper position in rod and

enough to slip over piston and into correct groove. Number 2

cap. Position caps on studs of connecting rods with identifying

compression ring must be installed with scraper edge down

number on cap on same side as number on connecting rod

(figure 4-22). Use a suitable ring compressor for installing

(figure 4-15). Tighten connecting rod nuts 28 to 32 foot

pistons in cylinders. Stagger piston ring gaps 90 degrees

pounds torque then install palnuts and tighten with wrench to

around piston. Oil pistons, rings, wrist pin, rod bearings, and

1/4 turn beyond finger tight position.

cylinder walls before assembly. Be sure arrow on top of piston

(6) Position oil pump in crankcase and attach oil

is pointing in direction of crankshaft rotation (clockwise when

pump drive gear (figure 4-10) with lock nut. Tighten oil pump

viewing flywheel end). Be sure piston and connecting rod

lock screw with 5/32 inch allen wrench (figure 4-13) and install

assemblies are installed into same cylinder from which they

slotted pipe plug. Install oil pan with deep end toward oil

were removed.

pump. Tighten mounting screws 6 to 9 foot pounds torque.

(7) Install idler gear and shaft in crankcase. Be sure

oil groove in shaft is facing up. Drive shaft into crankcase with

soft metal hammer and maintain a 0.003 to 0.004 inch

clearance between idler gear and shoulder of shaft. Install

setscrew (figure 4-11) on magneto side of crankcase to lock

idler shaft in place.

Figure 4-20. Adjusting Tappets

Figure 4-22. Piston Ring Positions

4-12