Cycle News - Archive Issues - 1980's

I I (Left) At tint. 1E8gIm'. Hewk doeIn't look too different from ItOCk. .-ndUng Improvementi mild. up the bulk of mods. engine (right) Ian't hopped up recIIc:eIy• Pat Eagan r~veals the secrets of his AFM Champio~ship-winningHonda Hawk By Pat Eagan In California, the American Federation of Motorcyclists' medium displacement (350430cc) Production class had been dominated by RD350/400 Yamahas since 1971. In fact, the last time a race in the category was won by a four-stroke was mid-1972. The Yamaha domination was brought to an 10 end this year by a Honda Hawk owned and ridden by Pat Eagan. A Cycle World Magazine project bike in 1979, the Hawk did not ~ach full bloom until 1980 because of a scarcity of aftermarket parts. The bike ran almost the enti~ season with stan· dard pistons because there were no others available. The only successful engine modification that year was the installation of a Mega Cycle camshaft. pan number 36x1. Q.uaner mile performance was improved from 14.1 seconds at 91 mph to 15.7 seconds at 95 mph. Impressive for a single modification but not enough improve· ment to deal with Yamahas which we~ turning 12.8 seconds at 102 mph. The frustrating season came to an end with an up-beat when a package from Moriwaki Engineering in Japan arrived with a piston kit. catnshaft. and oversize valves. Unfonunately. Cycle World had decided they had tuen enough abuse for one year and elected to discontinue the project. I still had faith in the potential of the Hawk and purchased the bike. Moriwaki pressure·casu his pistons. This technique resulu in pistons which a~ very strong and yet lighter than stock. These pistons a~ 2.Smm larger than standard bo~ 73mm but because of p~u~ casting are two ounces lighter (8 oz. with wrist pin and rings, compared with the 10 oz. stock uniu). The oil control ring is the usual three piece affair but only one compression ring is used; it's a Dykes type. Compression ratio is higher at 10: 1. Kaz Yoshima of Ontario Moto Tech modified the cylinder head to accept the one millimeter overize intake valves and assembled the top end. Exhaust valves are standard size but a~ recontou~d and polished for improved flow. Norris Cycle Producu valve springs and titanium retainers a~ used. and the springs are packed so that the~ is .040" to .100" oftravelleft at full lift. The head modification is very mild, and Kaz claims the~ a~ two to three more horsepower to be found in the motor. Ontario Moto Tech is the im· poner and distributor for Moriwaki parts. These pans can be ordered directly from them or through your local dealer. After the Morlwaki motor was broken in. a day was spent at the drag· strip playing with the airbox and the main jeu. The best run was 13.3 seconds at 96 mph. The peculiar dis· covery was that nothing could be done to the airbox to improve the times. Main jet sizes could be changed to compensate for the removal of the air cleaner. etc., but the stock airbox is good. The only reliability problem in two years' racing were incurred because of transmission selector problems. The stock five·speed will occasionally miss the founh or fifth gear shift or "warble" up and down in between. The fint attempt at curing the prob· lem was to shim the stationary gears closer to the sliding gears and inc~as· ing the p~u~ of the detent spring and polishing the det~nt cam. This was only partiy successful, and a year later the motor jumped out of gear and the balancer chain disintegrated. The final CU~ was to take the trans· mission shaft with founh and fifth on it to VHR (Vance at Hines Racing) to have them undercut the engagement dogs. It was surprisingly cheap and ~nally effective; no shifting problems SlDce. Otherwise, with the exception of the Barnett clutch, the motor is stock. To compensate for the non·adjustability of the ignition timing, high octane gasoline. such as Oaeco or SoCal Blue, must be used. All stock ignition com· ponents are used to fire the Nippon Denso "Hot U" spark plugs. Heat ranges used are X·27ES·GU for Sears Point and X·3IES·GU for Ontario and Riverside where there is more sustained wide open throttle. In three years of using NOs, I've not had one spark plug failure of any kind. AFM rules allow ~positioning of the exhaust system for the purpose of gaining cornering clearance, but on the Hawk this is impossible because the power chamber bolu directly to the underside of the engine. Because of this. the only way to gain the needed clearance is to raise the bike. Extend· ed damper rods inch longer we~ made up to raise the front of the bike. At the time we were doing this project. there were no aftermarket shock abo sorbers until we got the damping rates right. Looking at dyno graphs and talking with Bob indicates that SatW used the rates on these shocks for the production shocks that you can buy. The main difference is that my shocks are inch longer than stock, again to gain ground clearance. With a dry rider weight of 150 pounds. 80 pound springs a~ used in the rear. and stock springs in the forks. Kal-Gard's 15weight fork oil with Molybdenum Disulfide is used. Preload is set at both ends so that the bike sags approximate· Iy an inch when the rider sits on the bike. A lot of controversy was generated this year by my choice of wheels. The AFM rulebook says that aftermarket wheels may be used but does not specify either that the wheels must be castings or catalogued. All the rulebook says is that they must bolt up to the stock. un· modified brake and drive componenu. The purpose of the rule is to allow competitors to get the proper rim sizes to correspond to the slicks we must use. Working within this framework and intent of the rule. I had a couple of wheels made up so that I could have a WM5·19 rim on the front and a WM4· 18 rear. Meryl's Pro Wheel manufactured them using 0.1.0 rims and his own stainless steel spokes. 8·gauge front, 7·gauge ~ar. The front hub is a '79 750K Honda because the disc rotor bolts right up while the rear hub is Hawk Type I. On the front hub. the surface that the disc bolu to must be machined approximately .100 inch to get proper spacing. Tires used we~ Goodyear. 3.25x19 and 3.S0xl8. * * One situation that needed to be changed on the stock Hawk was the placement of the footpegs and brake pedal. With the stock brake pedal wrapping underneath the exhaust pipe, not only do you have decreased ground clearance. but. to me a worse problem. I like to be able to use my brakes any time I need to, and that might be while I'm all leaned over in the middle of a right hand comer. Terry Moriany of Alloy Graphics made the pedal and cable receiver. The pegs we~ ~itioned ~arward two inches and up an inch. Rideability is what this Hawk is all about. The changes I made were almost all aimed toward making the bike mo~ controllable. Changes to the chassis we~ to gain cornering clearance and traction. Function is the point. The engine is in a very mild state of tune. The powerband is ~ally similar to a stocker. When ridden around town, the motor pulls from extremely low revs even though the bike is geared up, (up one tooth on the countershaft, down one on the ~ar). With this gearing, it feels like the bike is geared low, but it's not. Top speed as geared is good for over 115 mph. Power is IIIellb1e from just above idle and notice· ably comes on at 6,500 rpm. Shift point is 11.000 rpm. If necessary. the motor will rev higher, but because of the stock carbs and exhaust system. there is no ~al power up there. I won seven races and' the 430cc Production Championship with the Hawk this year. and the ~ason is that the bike is a total package. The only area where the bike is singularly superior to the RD Yamahas is acceleration away from the staning grid and off the comers. The reason for this is fOUT'stroke torque combined with a fairly heavy flywheel. Exiting a comer. the flywheel enables you to apply mo~ throttle earlier without fear of the rear ti~ spinning. And when the tire spins, it's mo~ controllable. The bike is 50 to 50 pounds heavier than most of the RDs but it doesn't seem to make that much difference. I hope that what I've done this year will open up the most popular class at the club races and put an end to the single brand domination. Ontario Moto Tech 6850 Vineland Ave•• Unit 16 No. HoUywood, CA 91605 2131766-7101 Vance Be Hina Racing 14010 Marquardt Santa Fe Springs, CA 90670 215/921-7461 AlIoy Graphia 11512 E. 2Uth St. Lakewood, CA 90715 215/860-8351 Meryl'. Pro Wheel 2899 E. Coronado St• Anaheim, CA 92806 714/~15 •

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