All Harley-Davidson crank pins, roller bearings and crankcase bushings are lapped to a glass smoothness. Manufacturing practice which only grinds leaves irregular bearing surfaces. Close scrutiny reveals hills and valleys. Without lapping, thousands of miles of road service are required to eliminate these grinding marks. Lapping operations give owners maximum performance from the very outset and greatly prolong motor bearing life.
Chrome name-plates grace the sides of the tanks of all Harley-Davidsons for 1940. The 61,
Now, the crankcase main bearings of the big twins feature a straight-through lap, the same as on the 45 twins and Servi-Cars. This involves a change in the gear and sprocket side crankcase bushings so they can be lapped at the time they are assembled. Perfect alignment of main bearings results, heat is reduced, and bearings are kept from crowding and creeping.
More power has been designed into the 1940 61 OHV. First of all, the bore on the Linkert carburetor is now 1 1/2” in diameter -an increase of 1/4”. The venturi of the carburetor is now 1 5/16” in diameter-an increase of 1/4”. The manifold is 1 9/16” in diameter instead of 1 3/8” as formerly. In addition, the manifold is now T shaped instead of modified Y. It is smooth-bored and gas mixture flows rapidly and easily. Cylinder heads have been provided with larger intake openings to accommodate the larger manifold and carburetor. All these changes bring the gas mixture more quickly and in greater quantity to the combustion chamber, and this, of course, is translated into more horsepower and acceleration.
Rocker arm shafts have been changed so it is unnecessary to make adjustments in order to get the proper amount of oil to the rocker arms. Location of holes in the rocker arm fingers has been changed to insure positive lubrication. A constant, ample supply of oil is assured for the overhead mechanism, and adjustments are eliminated.
The relay base plate on the 61 OHV motor has been redesigned to accommodate the chrome stack on the front exhaust pipe. This gives needed clearance and prevents shorting from the relay to the stack.
45 twins and Servi-Cars for 1940 are fitted with a clutch key ring that features six inser
Safety will be promoted and better and easier brake action will be obtained with the advancement incorporated in the front wheel brake drum on the big twins and the drums on the rear wheels of the Servi-Cars are made of cast nickel iron instead of stampings. Being cast, and having ample cross section with an integral stiffening ring on the outside diameter, vibration and chatter are eliminated. The inside brake shoe surface is ground absolutely smooth for easy operation. A more efficient braking system results and the rider has a greater margin of safety at his command.
Still another change is being featured in the front wheel brakes of the big twins and the rear wheel brakes of the Servi-Cars, made possible by the new cast drums. As there is no deflection in these new drums, it is possible to employ a 9/32” narrower brake shoe operating shaft. This makes for smoother braking leverage, and it is easier for the rider to expand the brake shoes and make them effective.
Ribbed crankcase and aluminum heads distinguish the 80 in. Twin motor
Shifting has been made faster and smoother on 45 twins and Servi-Cars by incorporating a spring-loaded ball shift lock in place of the former pin lock. Positions on the shifter drum are easily located. The cam plunger ball is made of chrome alloy steel and is 1/2” in. diameter. Spring tension on the ball can be easily adjusted. This method of locking the shifter drum is now the same as that incorporated on the big twins. The faster, easier shifting of gears that results will be much appreciated, especially by competition riders.
The gear shifter fingers on the 45 twins and Servi-Cars are fitted with rollers which will free their movement on the shifter drum. Slots in the drum have been widened to accommodate the new design. Friction has been reduced, shifting facilitated, and added service has been given these parts. Gear shifter finger design is identical on all models.