Saturday, January 2, 2016

Harley Davidson JDH...

The Harley Davidson JDH two cam road bike was perhaps the coolest thing that ever came of  Milwaukee .  It was only made for two years in the road going model but had deep roots going back to the factories race bikes.  It was replaced in 1930 by the VL which was about as fast but the engine lost something in the style department.

In its day, the Harley-Davidson JDH, better known simply as the Two-Cam Harley, was the fastest road bike the company ever offered to the public and likely the fastest bike on the streets period. Reportedly it could attain speeds of 85 mph and could even be coaxed to 100 mph with tuning. Only the Henderson KL would have been capable of fending off a fast Two-Cam.

The Two-Cam engine had earned a lasting reputation for its power and acceleration in racing. Harley-Davidson had provided the ultimate motorcycle by joining its specialized racing engine with the chassis of their standard JD street motorcycle. Nearly 24,000 motorcycles were produced by Harley-Davidson in 1929 and over 10,000 of those were 74ci JD’s, yet there were probably less than 100 of these very special H models were ever built. There weren’t even enough for each dealer to receive one. If you could locate one to purchase, the buyer had to be ready to plunk down $370 for the privilege to own one. A lot of money in those days, this privilege was $50 over the value of a regular JD.

Excepting the unique motor, the 1929 JDH was identical to the standard JD model. The JD was the first Harley-Davidson that took on the appearance of a modern motorcycle, mostly through styling changes such as larger fenders and gas tank. The bike rolled on 18 inch wheels that minimized the ‘antique’ look. New for 1929 were twin bullet headlights. While not very effective, they were definitely trendy. A new instrument dash with the machine’s switches and ammeter modernized the bike as did covering the oil pump on the side of the timing case. Social responsibility was just as important in 1929 as today, and the motorcycle featured quiet 4-pipe mufflers. Carried over from 1928, a front brake became standard equipment.

The Two-Cam motor had its heritage in racing. Using two camshafts instead of a single shaft allowed the valve train to be smaller and lighter enabling the motors to spin faster than the stock JD engines. However reliability probably suffered as the exposed valve assemblies were noisy and prone to excessive wear from road dirt. Like the JD, the JDH was the final gasp of the 74ci F-head engines to be produced by Harley-Davidson. The following year, the sidevalve motor would be fitted in all models of the company’s bikes. The industry would have to wait until 1936 when the introduction of the Knucklehead would cause the same kind of excitement with riders.

 A nicely restored JDH

A JDH race bike with overhead valve set up

A custom JDH

The first time I ever noticed a JDH was when I watched the Rocketeer years ago, it only in a few scenes but stood out to me.  When I lived in Albuquerque, NM later on I saw a JDH on display in the local Harley Davidson dealership and it was the same bike as used in the movie according to the owner.  It probably was as there were never very many originals built and at that time I don't believe anyone was reproducing them.