Hercules Factory Isdt 100
CYCLE WORLD ROAD TEST
"A Wonderful Bird Is The Pelican
MOST OF OUR READERS have never had the opportunity to go overseas to witness the king of enduro-type events. And it's a fairly sure bet that we’ll be sporting a few grey hairs before the FIM even considers the United States as a possible venue for the International Six Day Trial, so it is no surprise that the ISDT remains, for many, a distant, abstract thing. Thus, you may ask, “Why all the fuss about an overblown enduro? Why should the machinery be so special if all one has to do is move from Point A to Point B in a specified average time?”
There are three basic reasons. First of all, the trial lasts an agonizing six days, and runs over about 1,000 miles of mostly off-the-road course — roughly akin to riding from Florida to Maine without using the highway. Secondly, unlike an AMA enduro, the ISDT allows arrival at a checkpoint early, without penalty; as this rule gives the Six Days man much needed time to work on his machinery, speed is at a premium. Also, special scrambles, braking and road race sections increase the emphasis on high performance of engine and suspension.
HERCULES FACTORY ISDT 100
As the ISDT has considerable advertising value in Europe, particularly for lightweights, manufacturers dote on the machinery they enter, producing one-offs that are as exotic as factory road racers. Just how different? Well, Americans who have been honored with factory ISDT rides are generally enraptured by their mounts. Ask Char lie "Hockie" Hochderffer about his "Herc."
What they had to say whetted our appetites, so w~ offhandedly (but breathing heavily) dropped the hint to the Hercules people that CYCLE WORLD would like to have its own "factory ride" to see just what made these diminu tive machines so fabulous. Surprise of surprises, word got back to us that the very machine on which Hockie silver medaled the 1966 ISDT would soon arrive from West Germany by airmail!
However, as a condition of receiving such a great honor from Nurnberger Hercules-Werke GmbH, we had to vow not to open up the 100cc class powerplant and look at the top-secret porting therein, cross our trials suits and hope to die. To ensure that our mechanical curiosity would not compromise our integrity, the clever chaps at the Herc plant replaced all the parts that Hockie had managed to demolish during his ride and then painted coded seals per ISDT procedure so that we couldn't sneak a look without tipping our hand.
How amazing it is, the honesty one must display un der such circumstances! Therefore, we must dolefully ad mit to guessing a bit on the inner workings.
The engin~ is a 97cc Sachs two-stroke, Hercules be ing a subsidiary firm of Fichtel & Sachs, an automotive firm which supplies engines to other European manufac turers (some of whom also field ISDT entries) and which, incidentally, mass produces the revolutionary "Wankel" rotary piston engine. The Herc's bore-stroke configuration is "undersquare" at 48mm by 54mm, the same dimensions used in their production 97cc four-speed trail bike, which was first introduced in the states as Rabeneick. We theorized that the long stroke might be one of those "mother-is-the-invention-of-necessity" things - an attempt to stroke a smaller displacement model. A further look at the Hercules line would negate this theory, as the company's 50cc production five-speed scrambler has a longish 44mm stroke, compared to its 38mm bore. It is odd that both the ISDT and produc tion one-hundreds share the same designation, K-103-GS, as the similarities are a bit vague. The ISDT model, rated at 12-1/2 rear wheel bhp, gets about 50 percent more power than the production job and has a six-speed gear box which allows it to be stump-puller and still top 70 mph with the proper overall gearing. This latter character istic was demonstrated quite graphically to our publisher during the 1966 ISDT; driving a fast Swedish touring car through the rain to reach a checkpoint, he could not stay with a similar Herc and two other competitors of the same displacement. The six speeds, of course, are a de light on a bike this size, as one never runs out of power, no matter the speed. It should be noted that 12-1/2 bhp is not an incredible figure, for a few other marques in production may be backyard-tuned for more than 15 bhp. However, engines tuned to this state are "pipey" and fussy, whereas the Herc produces usable torque from idle through buzzing range, and starts easily, rain or shine. Therein lies the possible reason for all the secrecy.
The manufacturers did tell us that both upper and lower ends of the connecting rod run on needle bearings, which is unusual practice for an engine this small. The crankshaft runs on ball bearings. The piston is aluminum with two rings and gives a compression ratio of 9.5: 1. The cylinder is made of “special” cast iron, the factory tells us; this probably translates as austenitic iron, which has an expansion rate approximating that of aluminum.
As Sachs generally turns to Bosch for ignition, we may safely guess, without prying the cover off, that the Here employs a Bosh flywheel magneto. The rationale in the engine’s basic features seems not to be for sheer power, but for reliability. After all, this machine will be operating at “nine-tenths” for 1,000 absurdly rough miles with minimal maintenance, left out in the open overnight, yet expected to kick-start each morning in less than one minute. Thus, we can also assume that the ignition has been waterproofed internally; externally one can see the precaution in the double wrapping around groups of exposed wires. Similar weather protection appears in the unusually long rubber “sock” running down the throttle and choke cables to cover the carburetor top, and in the plastic “baggy” shrouding the float bowl.
The ISDT model’s frame also has some similarity to that of the production bike, mainly in the single, massive, central backbone which runs back and down from the steering head to the swing arm assembly. But, on the ISDT Here, an “afterthought” double loop cradle appears, bolted to the steering head up top and to the footpeg mounting assembly down below.
Rear subframe treatment is roughly the same as that of the production bike, although the ISDT model’s horizontal seat cradle tubes projecting backward from the main backbone join in the rear to form a continuous loop. These form the upper sides of triangles utilizing the backbone and tubes extending from the swing arm assembly to the upper rear shock absorber mounts. The swing arm, mounted outboard of the assembly, is beefier and longer than those on some production “dirt” 500s we’ve seen. The wheelbase is surprisingly short for what amounts to a scrambler with street equipment. But, as the machine seems stable enough in bouncy terrain, save for the rear end’s tendency to deflect easily, we must conclude that Hercules has successfully applied the principle used by a few other manufacturers who have been successful in international motocross — i.e., short-coupling combined with extreme rake and ample swing arm length. However, the machine seems a little heavier than it need be for its class, even if one takes into account the fact that it is running headlight, stoplight, horn, and tire pump.
Front suspension consists of the heavy but effective Earles-type leading link forks, set for a good deal of rake and trail, and offering effective wheel travel of about five inches. Rear suspension units are, oddly, British-made Girlings. While damping fore and aft seems good, the total effect is a little harder than we would like it, were we contemplating six days of breakneck travel. This is sure to be compounded by the Teutonic practice of running high tire pressures from 20 to 26 pounds (which is also an explanation for the absence of rim locks on both front and rear wheels). Use of the 2.50 by 21-inch tire up front is Standard practice and offers very precise steering. This, and the choice of Metzler sports tires, makes the Here a dream in the mud.
Now we come to the little features that may mean the difference between winning and losing. For example, the Magura controls are quite pliable; if the rider does something naughty and bends them, chances are he’ll still have controls when he attempts to bend them back. The folding footpegs, rather than being externally sprung, have the return spring in the hollow of the pegs, where they are unlikely to be cracked or detached by rocks or branches.
The entire center frame section is utilized for the still air box, so there is virtually no restriction for the carburetor. The air cleaner canister is mounted under the gasoline tank and the paper element filter is easily replaceable by loosening a leather belt and lifting the tank. Assuming that other elements in this engine will not wash out easily, the high position of the air box mouth would allow one to ride the Here in mud and/or water 2-1/2 feet deep before the wrong thing went down its windpipe.
The reader may not find it easy to like the Here’s appearance, which prompted one of our staffers to call it “The Pelican.” However, this is one case where form becomes subordinate to function and produces a new kind of beauty.
HERCULES FACTORY ISDT 100
SPECIFICATIONS
POWER TRANSMISSION
DIMENSION, INCHES
PERFORMANCE
