From the October 1940 Issue of Motorcyclist Magazine
Harley-Davidson has announced a 74 cu. in. o.h.v. model for 1941, of which a limited number will be produced. With a bore of 3-7/16” and a stroke of 3-31/32” this new job is intended to furnish all the advantages of the 61 cu. in. o.h.v. but has added power sufficient to handle a sidecar easily, and “a solo motorcycle with performance far beyond ordinary requirements.” Connection rods on the 61” and 74” are identical.
Among the basic changes and improvements for ‘41 is a centrifugally-controlled oil pump which is to be a feature of all models. The centrifugally-controlled bypass valve regulates the flow of oil to the motor according to the speed of the engine. At high speeds more oil flows into the motor. At low speeds oil is diverted in larger quantities to the gear case and back to the supply tank with less oil passing into the motor. This is a guard against fouled plugs and excessive carbon formation which might result from over-oiling at slower speeds. The vane type pumps of the 45, 74 and 80 side valve motors, and the gear-driven pumps of the 61 and 74 o.h.v. motors incorporate the centrifugally controlled by-pass valve.
A new design clutch goes on the 61, 74 and 80 side valve twins. The clutch assembly has three steel discs, three friction discs and one spring disc. In addition to the three fibre or friction discs, the spring disc also has a fibre facing, giving the clutch the benefit of an additional frictional surface. There are a total of seven frictional surfaces as compared to five in 1940. The frictional area is 121 square inches, 48 square inches greater than previously, or an increase of 65%.
To overcome sticking and grabbing, milled splines in the key ring are eliminated and six hardened-steel keys riveted to the key ring are substituted. Ten driving pins on the clutch hub now take the place of splines on the hub. The three steel discs are driven by the keys in the clutch key ring, and the fibre or friction discs drive through the driving pins on the clutch hubs. Looseness and resulting rattle in the clutch plates are compensated and obviated by two spring-loaded balls on each steel disc.
The clutch hub is new, larger, and has 36 ball bearings arranged in two staggered rows, still further assuring smooth clutch operation. Each of these balls is 7/32” in diameter and each is individually retained. The staggering of these rows gives the effect of four rows of balls. By contrast, the 1940 clutch hub had two straight rows of ball bearings, with smaller balls 3/16” in diameter and were not individually retained.
The clutch for the 45 has also been redesigned, though it is proportionately smaller. It has two fibre discs and one spring disc. It also has six frictional surfaces, including the backer friction disc and a frictional surface on one side of the spring disc. The fibre discs for 1941 are mounted to steel discs the same as in the Big Twins. The new design enables the working parts of the clutch to travel back and forth from a released position to an engaged position more freely. The spring load required to operate the new 45 clutch is approximately 300 pounds, as compared to a spring load of about 500 pounds on the 1940.
The hub of the new 45 clutch is larger than its predecessors, has two staggered rows of 36 steel balls, each ball 7/32” in diameter and each individually retained. The hub is fitted to the main shaft by means of splines. Formerly it was fitted to the main shaft by means of a taper and a key.
Transmission gears on the 45 and Servi-Cars have been strengthened and their diameters increased. Dog clutches are heavier and their diameters increased. Gears are slightly farther apart for easier adjustment. Easier shifting is accomplished thru a redesign of transmission cam and shifter lever gear. The ratio of the shifter lever gear is increased and the track of the shifter cam lengthened.
The clutch release lever on 4Ss and Servi-Cars has been made larger and is now straight in shape. A stranded steel cable connects the clutch foot pedal and the clutch release lever. The cable runs in a seamless steel tubing which acts as a guide. The clutch push rod bearing has been increased in size and is better shielded to keep out dirt and retain its lubrication.
A new type muffler is used on the big twins. A perforated steel tube runs through the length of the muffler. At the half-way mark, this tube is blocked, forcing the gases through the perforations into the outer chamber and then back into the rear section of the tube and out through the bullet end that blends into a curved fishtail. There is no steel wool to disintegrate, burn and blow out. The longer, effective length of this new muffler, plus its greater diameter, helps reduce the crack of the exhaust, giving it a lower tone than formerly.
Large silver numerals and a white pointer with triangular sides characterize the speedometer dial on all models. The white triangular sides of the pointer pick up the light rays from the light source at the bottom and make dial reading easy at night. The glass, or bezel as it is also known, covering the dial is no longer flat but is now slightly convex.
An additional safety factor has been incorporated in the 45 Twins by a number of brake improvements. An extension of the chain line on the 45 Twins has made it possible to increase the width of the rear brake drum and of the brake shoe and lining. The top of the brake lever arm has been offset to allow for the increased width of the brake drum, thus maintaining the lever in its former position. Braking area has been increased 44%. Brake lining life has been materially lengthened because heat is now dissipated over a larger surface.
The use of heavier gauge metal and a slight change in shape have greatly strengthened the front brake shell on the 45 Twins. The stiffer shell prevents distortion of the wheel after it has been spoked and trued.
All the 1941 Harley-Davidsons feature a hand brake lever of new design. The new lever, made of die-cast aluminum, is longer, fits the hand, and provides greater leverage. The lever bracket is also of die-cast aluminum. The rotating stud at the pivot point of the lever permits the cable to enter the conduit without kinking or bending, and eliminates cable abrasion and wear.
The bearing on the big twin clutch foot lever has been lengthened. The clutch release lever is made in one piece.
The air cleaner available in the sport solo and deluxe solo groups, while of the same design as formerly, has been increased a full inch in diameter. The increased diameter makes possible the use of a larger air cleaning pack with consequent decrease in the velocity of the incoming air. Oil is retained longer in the mesh pack and is not drawn into the carburetor. The cleaner position has been moved down so carburetor adjustments can be made more easily.
Scuffing and the formation of ridges in the cylinder walls of all 1941 motors will be greatly reduced by the use of oxidecoated piston rings. Longer ring life results and better motor performance naturally follows.
Gear shifter levers are now made from a special steel that is cyanide-hardened. The new levers will not wear and cut through at the gate.
Batteries are now grounded on the frame where heretofore they were grounded on one of the oil lines. A better and more satisfactory ground for the battery is secured.
A heavier clamping ring in the horns of the 1941 models prevents distortion of the diaphragm when mounted on the motorcycles. Horns will consequently function as well at high speeds as at low Speeds. Horn tone is at a slightly lower pitch and is more pleasing.
The instant gas reserve valve and the interconnected tanks introduced on the Big Twins last year are features that have been retained. The only change made for 1941 has been to redesign the gas valve stem so that a full gallon of gas is retained in the reserve.
The streamlined tool box featured on the Big Twins the past year is now also incorporated on the 45 solo Twins.
The rear safety guard for the 45 Twins, obtainable as an accessory item, has been redesigned to prevent interference with rider’s leg when he uses the kick starter. Transmission kick starter springs on the 45 Twins have been redesigned. They will give better and longer service.
The round, rubber-covered steel support for the transparency of former summer shields has been eliminated. Instead, the transparency is held rigid with a narrow stainless steel edging. The bottom is secured with a 1/2” stainless steel moulding. The inside frame is made of spot-welded, chrome-plated steel. The shield can be placed in five different positions to suit the rider’s individual requirements.
The transparency in the new 1941 summer sport shield is Plastacele, .060” thick. This is twice the thickness of the pyralin used in the former standard shields. Plastacele is not affected by the rays of the sun, does not get brown, brittle, or crack. The fabric in the new shield is rubber-coated on both sides in a silver finish. The fabric apron is reinforced around the edges with coiled steel wire similar to control wire. The wire is fabric-covered.
Prices are reduced on two models and maintained on others. The 61 cu. in. o.h.v. is reduced $5.00 and the WLDR is reduced $10.00. The latter is now a regular road model. This job develops approximately 7 more horsepower than the WLDR and peaks around 5500 to 5700 r.p.m.
Color options for 1941 are the following: Skyway Blue, Cruiser Green, Flight Red, Brilliant Black, Police Silver (Police only).
Centrifugally-Controlled Oil Pump on All Models; New Design Clutch on All Models; Improved Transmission on 45 Twins and Servi-Cars; Improved 45 Twins and Servi-Car Clutch Releasing Mechanism; New, Quiet Big Twin Muffler; Airplane- Style Speedometer Dial; Improved 45 Twin Brakes; Positive-Grip Hand Brake Lever; Redesigned Big Twin Clutch Foot Lever Assembly; Giant Air Cleaner; Oxide-Coated Piston Rings; Hardened Gear Shifter Levers; New 45 Twin Tool Box; New Front Wheel on Servi-Cars; Relocated Police Radio Carrier; Classy Summer Sport Shield; A New Model-The 74 OHV; Beautiful Color Options; Lower Prices on 61 OHV and 45 WLDR.