Harley-Davidson WLA Technical data
(from service manual TM 9-1879)

Description and engine data
The vehicle is powered by a two-cylinder, V-type, L-head gasoline engine, operating on four-stroke, four-cycle principle. The bearings, pistons and rings, cylinder walls, bushings and gears are lubricated by a force-feed circulating oil system. Engine oil supply is maintained in a separate tank. Tolerances and fits are held to close standards, calling for precise and fine workmanship on the part of the mechanic

Fuel and intake systems

Fuel system. The fuel supply is kept in the left side tank and is gravity fed to the Linkert model M88 carburetor which is located between the engine cylinders. A supply valve is located in the tank and a strainer is located at carburetor bowl intake. The carburetor os of the side-outlet, plain-tube type with a fixed venturi. Carburetor has two manual controls, the throttle, which is operated by the right handlebar grip, and the choke, wich is operated by a lever located in the front side of the carburetor. The high speed fuel supply is governed by a fixed (non-adjustable) jet. The idling to medium speed, 30 miles per hour, fuel supply is governed by an adjustable (low speed) needle valve located on the rear side of the carburetor body.

Specifications for Linker model M88 carburetor

Carburetor Fuel Circuits. The motorcycle carburetor may be said to consist of four circuits. By describing and treating each circuit separately, study and repair of the carburetor is made easier.
(a) The Float Circuit. The float circuit consist of the bowl, the float, fuel supply valve and seat, and the circular cork float and lever assembly. The float circuit automatically controls the height of the fuel level in the bowl and also in the main nozzle.
(b) The High Speed Circuit. The high speed circuit consist of the main nozzle, fuel well, fixed metering jet, fixed size venturi, and the throttle dik. As the throttle is opened, the air flow over the main nozzle is increased, thus increasing the fuel supply which is atomized and vaporized on its way into the engine cylinders. The main nozzle is located in the narrowest part of the venturi, where the air stram through the carburetor is traveling at its greatest velocity.
(c) The Low Speed Circuit. The low speed circuit principal parts are: the mtering jet, fuel well, idling (low speed) needle and seat, supply channels and idle ports. The idling (low speed) circuit controls the engine fuel supply during idling and high load speeds up to approximately 30 miles per hour. The main metering jet supplies fuel into the well (same as in the high speed circuit) but with the throttle in closed position, the fuel is drawn off past the adjustable low speed needle valve, into the low speed channels (mixed with air from the low speed air bleed) into the carburetor bore through small holes and a narrow slot located at the edge of the throttle disk. The adjustable low speed needle valve controls the fuel supply feeding into the low speed channels. As the throttle is opened, the air stream through the venturi becomes more active, thus shifting from the low speed circuit to the high speed circuit.
(d) The Choke Circuit. The choke circuit is used to supply a rich fuel mixture, from which sufficient vapor will be obtained to start a cold engine. This circuit consists of a choke valve (disk) to close off partially all of the air supply through the carburetor bore, a shaft, lever, and cam assembly. The cam allows the low speed needle valve to rise off its seat so that the richer mixture can reach the idle holes. The choke lever is provided with several stops for full choke, starting, warming-up, and running positions.
Intake System. The intake system is extremely simple in that all units are exposed, closely connected, and readily accessible for operational service and/or repair. The intake system consists of an oil bath air cleaner, connecting hose, and carburetor intake fitting. The carburetor air and fuel passage connects with the two engine cylinders through a short intake pipe (manifold).

Exhaust system
The exhaust system consist of a muffler and tail-piece assembly, front exhaust pipe assembly, and rear exhaust pipe. Exhaust pipes are a slip fit in cylinder exhaust ports. The exhaust system is simple and efficient and readely accessible for service or repair.

Ignition system
This ignition system differs from the conventional automotive types, in that it has no high tension rotor or distribution cap. A circuit breaker (timer) alone is used. High tension cables lead directly from the spark coil secondary winding ends to the spark plugs, both plugs sparking at the same time. When one cylinder is on a compression stroke (ready for ignition), the other cylinder is on an exhaust stroke; thus only one cylinder fires when the circuit breaker points are opened. No. 3 spark plugs are used.

Generating system
The generating system consists of the 6-volt, shunt-wound, third-brush and "lamp-load" regulated generator, the storage battery and the relay. One of the two field coils (shunt coil) is controlled by the lighting circuit to increase the current output when either the running sevice light or the blackout light are turned on. The ignition- light switch cuts in the field shunt coil for the service light, and a magnetic field switch cuts in the field shunt coil for the blackout light. Maximum charge rate of 4 amperes (with service light on) is sufficient to keep the battery in a good state of charge under normal service conditions.

Horn and lighting system
The lighting system may be divided into two circuits: the service light system and the blackout light system. Both are master controlled by the ignition-light switch, and the blackout headlight is provided with an auxiliary switch. The panel switch has a lock-out feature, preventing use of the service lights until a button has been pressed to release the switch knob for the third, or service light position. The lighting system is related to the generating system an that either the ignition-light switch or a magnetic switch (for blackout headlight) cuts in the shunt field coil to increase the generator current output with lights on. The service headlight beam is controlled by a toggle switch located on the left handlebar.

Clutch
The clutch is of simple multiple dry-disk design with fiberglass plates and steel plates set alternately in the clutch shell. The disks are compressed by 10 heavy coil springs. One set of disks is connected with the hub assembly wich is secured to the transmission mainshaft gear. The other set of disks is connected to the clutch shell and sprocket assembly and is driven by the engine chain. The clutch is actuated by a rod which passes through the hollow mainshaft in the transmission. The clutch is controlled by the foot pedal located on the left footboard of the vehicle.

Transmission
Tranmission is of constant-mesh, progressive type. Gears are always in mesh and when shfting from low to high or viceversa, it is necessary to shift through neutral and second positions. Transmission is of thre-speed design and on WLA models, reverse gear is not provided. Sliding shifter clutches, actuated by the shifter drum cam, engage with dogs in the clutch gear and recesses in the second and low gears depending on the gear selected. Use of needle rollers, close fitting bronze bushings, and close tolerances necessitates use of engine oil for lubrication.

Brakes
Rear wheel brake. The brake is of the internal expanding, two-shoe, fixed-pivot mechanical type, operated by foot pedal on the right footboard. Brake shoes are centered within the drum by shifting the pivot. The shoes are operated (spread) by a cam which is actuated by the brake lever. Shoes are kept tight against pivot and cam faces by means of two coil springs. Adjustement is external, by altering lenght of break rod. Brake side cover is attached to vehicle frame, and drum is combined with the sprocket and wheel driving hub assembly. Driving hub also operates the speedometer drive gear.
Front wheel brake. The front wheel, hand-controlled auxiliary brake is of internal-expanding type. Two shoes, on a fixed pivot, are mechanically operated. Brake is controlled by a flexible streel wire (stranted cable) operating with a flexible housing. Brake drum is an integral part of the front wheel hub. Brake side cover is connected to the rigid fork by a shackle arm to allow for front fork spring action.

Chains, sprockets, wheels, and hubs
Wheel rims and spokes. Both wheels are wire spoked with 40 spokes in each. Front and rear wheels are not interchangeable. 18-inch drop center rims accommodate 18-inch x 4.00-inch drop center tires. Rims are interchangeable because of spoke nipple diameter and angles. Front wheel rim is identified by "SF 705 TA" stamped near the valve hole. Rear wheel has larger nipple holes and has number "XF 705" stamped near valve hole. Rims must be centered on hubs for correct alinement on vehicle.
Data.
(1) Front wheel
Rim, 18-inch, 40 holes (identified by "SF 705 TA" stamped near tire valve hole).
Spokes on brake flange side; 20 used, 5 ⁵/16 inches long.
Spokes on hub flange side; 20 used, 8 ³/8 inches long.
Nipples, 40 used.
(2) Rear wheel
Rim, 18-inch, 40 holes (identified by "XF 705" stamped near tire valve hole).
Spokes, 40 used, 8 ⁵/32 inches long, and 0.161-inch diameter.
Nipples, 40 used.
Wheel Hubs
a. Rear Hub. Knock-out axle with roller bearing hub. Fourteen 1/4- inch rollers used on brake end and twelve 1/4-inch rollers used on the other (outside) end. (Rollers are 0.490 in. long) End play adjustment is made by shims. Bearing wear is taken up by use of oversize rollers. To take up excessive side play only, it is not necessary to camplately disassemble hub.
b. Front Hub. Knock-out axle. Ball brearing hub, adjustable cone similar to bicycle hub design. Thirteen ⁵/16-inch balls used in each end. No ball ratainers used. Front hub and brake shell are integral construction. Grease gun lubrication.
Sprockets
(1) Engine Sprocket. Standard sprocket on WLA model has 31 teeth. Sprocket is 1/2- inch pitch for double-row roller chain and is taper fit on flywheel shaft with Woodruff key.
(2) Clutch Sprocket. The clutch sprocket is an integral part of the clutch shell assembly and also serves as outer race for clutch hub ball bearing. When worn or damaged, the sprocked and hub shell assembly must be replaced
(3) Transmission Countershaft Sprocket. Standard sprocket on WLA model has 17 teeth, sprocket is 5/8- inch pitch for single-row rooler chain and is taper fit on transmission mainshaft with two Woodruff keys.
(4) Rear Wheel Sprocket. The 41-tooth, ⁵/8-inch pitch sprocket is secured to brake drum with eighteen ⁵/32-inch rivets and six ³/16-icnh dowel pins.
Chains
(1) Front Chain. The front roller chain is endless, of double-row type, having 100 links of 1/2-inch pitch. Chain is lubricated from engine lubricating system and provided with separate adjustment. Front chain is adjusted by shifting transmission backward or forward in frame mounting.
(2) Rear Chain. The rear roller chain is a single-row, 5/8-inch pitch and is 58 3/4 inches long when new. Rear chain is secured on sprockets with a connector (master) link. Rear chain is lubricated by engine lubricating system and provided with separate adjustment. Supplementary lubrication provided by external application or by soaking chain in lubricating bath. Rear chain is adjusted by shifting rear wheel axle backward or forward in frame stay clips.

Steering System

Fork. The WLA model fork is composed of two members; namely, the spring fork and the rigid fork. The spring fork consists of two spring fork side assemblies to absorb shock and recoil during service action. The rigid fork stem passes through the frame head and, with the two assemblies, attaches to the handlebars for steering. The rigid fork bearing in the frame head is provided by thirty 5/16-inch balls, cones and frame head cups. Lower ends of the springs and rigid forks are attached to rocker plates which provide the mounting and rocker action for the front wheel. Forks are heat treated and bent forks can be straightened and alined without preheating.
Frame Head Bearings. Ball cups are pressed into the frame head to hold fifteen ⁵/16-inch steel balls (without retainer), upper and lower. A stationary cone is pressed onto the rigid fork center stem for the lower bearing race to float on, and an adjustable cone screws onto upper end of fork stem for upper bearing race to float on.
Steering Damper. The steering damper is an accesory, manually adjusted to apply friction to the front fork and prevent vehicle wobble in rough terrain or at high speeds.
Handlebars and controls. Handlebars are of welded construction and are heat-treated for strength. Do not weld handlebars. The only repair that should be attempted is straightening of handlebars. The handlebar bracket attaches to the rigid fork side bar and outer stem ends. Control wire plungers (spark and throttle) are actuated by spirals in the grip sleeves. The grip sleeves are retained on the handlebars by means of end screws.

Chassis Parts and Equipement

Frame and tanks
Frame. Steel forgings, steel castings, and steel tubing are assembled and brazed together making the frame an integral part. Reinforcing is provided at vital points and the frame is heat treated for additional strength. A frame that is not too badly bent can be straightened and alined cold, provided suitable fixtures and alining devices are at hand. A broken frame, or a frame bent to such extent the tubing or castings are weakened, must be replaced in the interest of safety in service.
Tanks. Tanks are of welded steel construction. All fittings are either welded or riveted in place. The right tank is used for engine oil. The left tank is used for fuel

Mudguards
a. Front Mudguard. I f front mudguard is badly bent or broken, repair is not worth while because future service will be limited. If stays or stay brackets only are bent or broken, they can be replaced.
b. Rear Mudguard. The rear end of the rear mudguard is hinged to the front section. Broken stays or stay brackets can be replaced. If mudguard is badly bent or broken, satisfactory repair cannot be made.

Chain guards
a. Front Chain Guard. The front chain guard is in two parts, the outer (cover) guard and the inner guard. When chain guard is not too badly bent or dented, it can be straihtened and made serciceable.
b. Rear Chain Guard. The rear chain guard can be straightened when bent and a damaged mounting stud can be replaced.

Stands
a. Jiffy Stand. The jiffy (side) stand is used as a prop and can be folded up out of the way, before vehicle is put in motion. Repairs to the jiffy stand consist of parts replacement.
b. Rear Stand. Rear stands supports the vehicle in an upright position. Stand is of welded construction. A badly bent, twisted, or broken stand must be replaced because insufficient strength remains in a damaged stand that has been straightened or welded.

Skid Plate
When the skid plate becomes so badly damaged it cannot be assembled to the vehicle without unnecessary work and time, it should be replaced. Owing to design of skid plate, it is difficult to aline, once twisted.

Battery Box The battery box is of unit construction and othe than taking out dents, replacing cover hold-down bolts and repainting, it cannot be repaired. The battery box is in a protected location and battery acid corrosion causes the most damage.

Tool Box
Other than straightening a dented toll box and replacing a damaged cover, other repairs are not practical.

Footboards
a. Left Footboard Sidebar. The left footboard sidebar provides footboard and clutch pedal mounting. Badly bent or broken parts must be replaced. The footboards cover and the footboard hinges can be replaced. Both footboards are interchangeable.
b. Right Footboard Sidebar. The right footboard sidebar provides footboard and brake pedal mounting. Badly bent or broken parts must be replaced.

Saddle
A badly bent, twisted, cut or worn saddle cannot be repaired with satisfactory results. Replace any saddle considered not safe and serviceable.

Saddle Post
a. Spring saddle post can be taken apart, and broken, or damaged springs, spring rod, and fittings can be replaced
b. Saddle Post Adjustement. The spring saddle spring post is correctly adjusted for the average weight rider when the distance from end of plunger to adjusting nut is 11 ¹⁵/16 inches. To increase spring compression, turn adjusting nut to the right. To reduce spring compression, turn adjusting nut to the left.

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