39. DESCRIPTION AND DATA.

a. Description. This 2‐cylinder, V‐type, air‐cooled gasoline engine of L‐head design operates on the 4‐stroke, 4‐cycle principle. Flywheel and connecting rod assemblies operate on roller bearings. Engine is fitted with low‐expansion aluminum alloy, cam‐ground, horizontally slotted pistons and with deep‐finned aluminum cylinder heads. As viewed from left side of vehicle (drive chain side), rotation of engine is counterclockwise.

b. Lubrication system is of dry‐sump type, in which oil supply is maintained in a tank away from engine. Oil is circulated by a supply feed pump and a scavenger, return pump. This oil circulating system plays a most important part in cooling the engine as well as lubricating it.

c. Data.

40. TUNE‐UP.

a. Tune‐up consists of making correct adjustment to valve tappets, circuit breaker ignition points, spark plug electrodes: checking and correcting ignition timing; draining and flushing carburetor bowl; cleaning and flushing gasoline strainer; cleaning muffler outlet, servicing air cleaner, and adjusting carburetor.

(1) Valve tappet adjustment (par. 43).

(2) Circuit breaker point adjustment (par. 84).

(3) Spark plug service (par. 83).

(4) Timing ignition (par. 86).

(5) Draining carburetor bowl (par. 73).

(6) Cleaning fuel strainer (par. 72).

(7) Cleaning muffler outlet requires freeing outlet of carbon deposits, caked dirt, oil, etc., with blade of screwdriver, or other suitable tool. Do not enlarge outlet size when cleaning.

(8) Servicing air cleaner (par. 76).

(9) Adjusting carburetor (par. 68).

41. REPLACEMENT OF HEAD GASKET (fig. 15).

a. Removal. Refer to figure 15, illustrating necessary parts and units to be removed to perform this operation.

(1) Remove instrument panel cover (par. 119).

(2) Remove gasoline tank and oil tank (par. 107).

(3) Remove cylinder head bracket to frame lug bolt: this will free clamp which secures front spark plug cable. Pay particular attention to shim washers placed between cylinder head bracket and frame lug, as these washers must be replaced when installing cylinder head.

(4) Remove spark plug, or plugs.

(5) Remove cylinder head bolts, using head bolt wrench 41–W–1525. NOTE: On some 42 WLA models, plain washers (0.095–inch thick), in addition to regular (heavy) cylinder head bolt washers, were used to prevent cylinder head bolts from bottoming.

(6) Perform carbon removal (head only). Refer to paragraph 42.

b. Installing Gasket and Head (fig. 15).

(1) Clean top of cylinder. Apply a light application of grease or oil to both sides of gasket before locating on cylinder head. Place head on cylinder.

(2) Install head bolts, using heavy washers (also 0.095–inch thick plain washers, if any were removed). If in doubt as to use of 0.095–inch thick washers in addition to regular washers, measure depth of bolt holes in cylinder head. Head having hole depth of 31/32 inch must use the 0.095–inch thick washers in addition to regular washers. Head having bolt hole depth of 1¹⁄₁₆ inch does not require the 0.095–inch thick washers.

(3) Install cylinder frame bracket with the two long bolts, special (spool‐shaped) spacers, and flat washers. The spacers go between cylinder heads and frame bracket. A flat washer goes under the head of each long cylinder bolt, above the bracket; some engines may have flat washers between the spacers and the bracket.

(4) Tighten head bolts evenly to ensure a tight cylinder head joint. Use head bolt wrench 41–W–1525, first turning down bolts just snug, then tightening each bolt ¹⁄₈ to ¼ turn at a time, until all are securely tightened. If torque wrench is available, tighten head bolts to 60 foot‐pounds minimum, 65 foot‐pounds maximum tension when engine is cold.

42. CARBON REMOVAL.

a. At time cylinder head is removed for gasket replacement, carbon must be removed from head only.

43. VALVE TAPPET ADJUSTMENT (fig. 16).

a. Adjust Tappets with Engine Cold. Before loosening valve spring covers, a light application of oil around top edge of each cover will facilitate raising cover without damage to seal packing.

(1) Loosen valve spring covers; use tappet and valve cover wrench 41–W–3617.

(2) Before checking or adjusting tappet clearance, make sure valve is seated and that tappet is at lowest position, by turning engine ahead until like tappet (inlet or exhaust, whichever one is being adjusted) in the other cylinder is at highest position (valve fully open). Inlet valves are located nearest the carburetor manifold.

(4) Loosen adjusting screw lock nut (“2,” fig. 16) slightly before turning adjusting screw (fig. 16).

(5) Adjust inlet valve tappets to 0.004–inch minimum, and 0.005–inch maximum clearance between valve stems and tappet (“1” and “4,” fig. 16). Use thickness gage to determine clearance; recheck (correcting if necessary) clearance after lock nut has been securely tightened.

(6) Adjust exhaust valve tappets to 0.006–inch minimum, and 0.007–inch maximum clearance between valve stems and tappet. Use thickness gage to determine clearance; recheck (correcting if necessary) clearance after lock nut has been securely tightened.

(7) Before turning down valve spring covers, inspect paper gasket between each cover and tappet guide. If broken or damaged, fit a new gasket to prevent oil leak. Turn down and securely tighten valve spring covers.

44. REPLACEMENT OF OIL FEED PUMP (fig. 17).

a. Removal.

(1) Disconnect oil tank feed pipe at oil tank. Install nipple cap on tank nipple to prevent oil from running out, or drain tank. Disconnect oil feed pipe from oil pump nipple.

(2) Oil pump is secured to engine gear case cover by one hexagon head bolt and three nuts. Two of the nuts are extra long to provide wrench clearance, and their location should be noted so they will be put back where they belong when reinstalling pump. After removing screw and nuts, remove pump. Unless a new pump gasket is available, take care not to damage or break the old one, as this is a very special gasket concerning both thickness and holes provided for oil channels. A “homemade” gasket may put oiling system completely out of commission.

b. Installing Oil Pump.

(1) Clean surface of pump body mounting on gear case cover and see that gasket is in good condition. Clean face of oil pump body.

(2) Start pump on mounting studs, turn engine slowly and press lightly against pump until driving dogs on end of cam gear shaft line up with and drop into driving slot in oil pump rotor.

(3) Insert hexagon‐head bolt and lock washer, and install the three lock washers and nuts (two are long extension nuts) on pump mounting studs. Make sure to replace the two extra long nuts on the studs from which they were originally removed.

(4) Tighten mounting bolt and three nuts securely.

(5) Connect oil feed pipe to oil pump nipple. Remove nipple cap from tank nipple and connect upper end of oil feed pipe to this nipple. Tighten nipple nuts securely.