Harley-Davidson Styling For 1940

By Chet Billings

The big twins are more streamlined than ever. A look at the gear side of their motors show parallel cooling fins! They add to the appearance of these models and increase efficiency as well. There are eight, one-quarter inch wide, parallel cooling ribs on the 61 OHV and nine on the 74 and 80 twins. These ribs are 3/8” to 1/2” deep on the 61 OHV and 1/2 “ to ¾” deep on the 74 and 80 twins. Strength is added to the case and heat is dissipated.

Another “speed-lined” feature of the 1940 big twins is the tear-drop design tool box with parallel ribbed cover. The new tool box is located on the right side of the rear frame stay. Capacity is ample. The ribbing on the cover harmonizes with the ribbing on the crankcase.

New forks on the 45 twins and Servi-Cars give the front end of these models a new appearance. The new forks are tubular steel, identical in design with the forks that have been used on the big twins. The spring fork is made of seamless steel carbon tubing and the main fork of swaged, chrome-molybdenum steel tubing. The new forks are lighter; and reduced weight, of course, increases handling ease, especially on the solo models-a feature that will appeal to competition riders. Adoption of these new forks also permits the use of the same type handlebars used on the big twins.

Heat treating has always been extensively employed by Harley-Davidson to add strength and service to various component parts of its motorcycles. Now for 1940, additional strength has been imparted to the front forks of all models by heat treating them.

The 80 twins have deep-finned aluminum heads. They are designed to dissipate motor heat, and at the same time add to the general appearance of the motor.

These new 1940 heads made of high Silicon Aluminum Alloy have a 41.5% greater cooling area than the former cast iron heads. They are also 10 pounds 4 ounces lighter per set than the iron heads. The heads are provided with brass, cast-in, spark plug inserts. Brass, of course, is less apt to strip and cross-thread than aluminum. The deep ribs are also cross-finned to prevent ringing.

The 74 twins are regularly fitted with cast iron heads but can be obtained with the above aluminum heads at an extra charge.

The advantages of the aluminum heads on the 80 twins also apply to this season’s 45 WLD. Last year’s WLD Special, announced in the spring, is the 1940 WLD and not only features the aluminum heads but the deep-finned cylinders, large manifold, and large carburetor. Cooling fins on the aluminum heads average 2 inches deep. There are 19 parallel rows of fins on the front head and 21 on the rear head. These aluminum heads have 51.5% more cooling area than the 45 cast iron heads. They weigh 8 pounds and 2 ounces less per set than the iron heads. The 45 twin WL model and Servi-Cars are fitted with iron heads.

Improvements have been made in the 45, Servi-Car, and 61 OHV motors that equalize distribution of oil to front and rear cylinders. The rear cylinder crankcase baffle plate has been removed and the front and rear connecting rods interchanged. Half of the slot on the lower boss of the forked rod has been closed and both cylinders and pistons receive proper lubrication. Two compression rings and a lower oil control ring are used on both the front and rear pistons as well as on the 74 and 80 twins. This cylinder lubrication change is the same that was incorporated in the 74 and 80 twins last year, and all Harley-Davidsons are identical in this respect. The improvement is designed to increase speed, power and motor life.

On the 61 OHV, 74 and 80 twin motor the crank pin has been increased in section from 1 1/8” to 1 1/4”. The number of rollers has been increased from 42 to 54. The more rollers traveling on a larger diameter pin give greater bearing capacity and thus insure longer bearing life.

By Chet Billings
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