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Issue link: https://magazine.cyclenews.com/i/125688
outer cases, caged roUers supply support on the inner cases, and a fifth needle bearing is mounted in the primary drive cover. Lifters are oiled by positive lubrication right through the .rocker arms and onto the cams. The camshafts are driven by a double row of chain. In short, every feature of the motor appears to be designed for heavy use. Also, much room for modification seems to have been designed into the machine. Valves are mounted in the heads at very wide angles, leaving plenty of room in the center of the dome between the valves. Also, the iron skuUs around which the aluminum head has been cast are very thick, leaving much room for Right i. the stock Eagle piston. Left i. tha replacement part constructed from an M.C. for~ BSA Victor piston. The crown has been welded up and machined to its prasent size. Notice the heavy knurling on both skirts. Kyle lets hi. pistons fit loosely. relying on ringl for compression. enlargement. In fact, the combustion chambers were undersized, and when Kyle machined them out to match the cylinders in diameter, what had been ample room for larger valves became even roomier. Likewise, all ports and valve guides are designed so that plenty of cutting, repotting, and polishing is possible. So Kyle had not only an overhead cam engine of the right volume. He also had a motor he could modify to his heart's content. As we mentioned, the tuner' feels that breathing is of major importance in a hillclimbing motor, so for a description of his special preparations, it is only appropriate that we begin with the upper end.. Kyle machined out and recontoured the iron combustion chambers in the Eagle's head. Formerly, the chambers had been under-sized, their diameter being somewhat smaller than the diameter of the cylinders. This was done because a larger chamber contains more area, and therefore larger valves can be installed. Then the inlet ports and valves were enlarRed a fuU quarter inch each, from 1~ inches to 1 3/4 inches. Exhausts were increased from 1 5/16 to 1~ inches. The new valves to be installed began as 327 cubic inch Chevrolet valves, and were properly modified for contour and length. But the new combustion chamber size left a great empty area that the rather flat-topped stock pistons did not fill. The replacement parts are M.C. brand forged pistons for the BSA Victor, chosen by Kyle for their gcnerally correct sizc. ThEy did much to fill the necd, but still a considerable amount of material had to be built up on the crowns by heliarc wclding. Then they were machined to shape> with large flat areas ground away for valve clearance. Also the skirts were liberally knurled to help hold oil. FoUowing Kyle's tbeories, they are a very loose fit. He relies upon the rings rather that the piston fit for compression. With the loose fit, Kyle intends the motor to blow before a piston will overheat and stlc,k. Wrist pins and connecting rods are stock, though the rods are lapped for clearance. With the huge valves comes a healthy appetite. To satisfy it, the 1 1/8 inch pelLorto carburetors with rectangular slides have oee" replaced by 1'4 inch DelLonoswith separate float bowls. Properly modified for the fuel diet, they contain oversized jets. As is the practice with Class A hillclimbers, no kind of flow-restricting air cleaner is installed. Only a screened cap is used to discourage entry by small birds. Carburetor and exhaust tuning is purely mathematical, based on an article that onCI) appeared on the subject years ago in Hot Rod Magazine. Kyle said it made sense and went into great detail, so he filed it' away, assuming the au thor knew his business. With ho dynamometer available, Glen has had to rely upon such theoretical ,preparation, bu t performance has not indicated any real error in the installations. Some problem has bean experlenced with _ r on the stock rockers. Arrow incl_ ...... fuel-dilu1lld oil has fIoiled to properly lubricata. The results· of the mathematics are long velocity tubes on the DelLortos and megaphoned exhaust pipes. Exhaust pipe diameter at the head remains stock, but the length of the pipes as weU as the rate of magaphone taper have been determined by the Hot Rod article. Kyle suspects that after major engineering problems are solved, eventually the Eagle will have to go on a dynamometer for practical refinement. The unneeded electric starter was not included with the motor, and the generator went in like fashion, into the scrap heap. The absence of the two armatures probably removes abou t 15 to 20 pounds from the motor. Spark is supplied by battery and double points. Furtner weight is removed in the transmission. Everything is eliminated except the main shaft and one gear, giving the hillclimber a simple in-and-out box for transmission of power. This not only eliminates total weight; it also avoids the rotating weight and friction that absorb much valuable horse power. Early runs resulted in problems with the clutch. To strengthen the unit, Kyle has added one steel plate and one friction plate, and has upped the spring tension. Finally, a whole home-made unit may be necessary, but to date the beefed-up standard clutch seems to be working. Along with the gears and shafts in the transmission, shifting and kick starter mechanisms were removed to reduce weight. Starting is by a portable crank that turns the sprocket 'on the right side of the engine that originally held the starter drive chain. The clutch is engaged by a cable and lever mechanism operated by the Icft foot, leaving the rider's left hand free to .operate only the kiU button. The mild steel frame was designed and fabricated by Kyle according to a procedure developed over the years. Glen has his own frame jig consisting of a piece of chanel iron with mounts for front and rear axles. The length between the axles is based on much experience on the hills. The correct fork angle and length (also based on practical knowledge) is determined, the motor is set in the chanel-iron as far forward as possible, then the welding and bending begin. The sprouting result is a tw<>-piece Vincent-type frame bolted to the front and the rear of the motor and using the cases themselves as members of the frame. Furthermore, the frame that Kyle has completed may be modified" through the instaUation of rigid units or short shock absorbers. The whole rear section can move slightly on a pivot at the back of the engine, and small shocks mounted at the front of the upper rear frame tubes allow the rear section to work like a Vincent frame. However, early runs convinced Glen that suspension was not desirable for this particular machine. The shocks have been replaced by rigid tubes, and fmally a lighter and totally rigid rear frame section will be designed WId built. ~, for some reason, Kyle discovered that tJie Eagle worked better with a rear section about three inches longer than any he had used before. The front forks are made from BSA down tubes and BSA springs with home-made lower tubes. Total travel is three inches. Also, an Indian brake of about 1950 vintage is installed on the front to help with return trips down the hill. The front whee1 is a twenty-one incher. , ~ w Z w oJ C,) > C,) The LavenI.'. iron skull combustion c,,"mbar is undersized in stock form, leeving • lip (AI whose diameter is smaller than thIt af the cylinder (8). Scooping the skull out e.._ . larger combustion chamber, incre_ng v8lve .at diameter by • much _ • quarter inch, from di.merer (C) to diameter (0). The dotted line indicates the surface of the new, larger chamber and port. The rear hub was built by Kyle from aircraft aluminum and is basically a copy of a Vincent hub, though stronger. The only reliability problems with the exception of the clutch weakness have been the result of the use of fuel. Mainly, the fuel attacks and rapidly destroys the rubber cam chain tensioners. Kyle feels that either he will fabricate new tensioning discs from aluminum, or use none at all. The chain can be strung tightly, and tensioners may not be necessary on the brief runs. Also, the fuel rapidly dilutes the oil and wear has been experienced where the rocker arms ride on the- cams. Chrome plating has not solved this problem, and perhaps rockers will need to be built from different material. Unlike the tensioners. however. wear here has not effected performance. Also, an all new dry clutch assembly may come later. Although the 2.3/1 primary drive ratio takes some of the load off the clutch, Kyle still feels that a wet clutch is a disadvantage for a hillclimber. He states that puUing out of a clay pit with a heavily chained rear wheel probably puts much more load on the clutch and drive chain than any dragster ever experiences. Glen Kyle's American Elllie now weights about 330 pounds wet. This is fIVe poundS more than his old Vincent, and even that, he says, was on the heavy side. However, properly distributed weight can be an advantage to a hillclimber if the motor is powerful enough to move it. Horsepower for the 750cc engine has reached about 90.