Triumph 500 Road Racer
TRIUMPH 500 ROAD RACER
No Rest For the Winner
THAT A TRIUMPH REPOSED in the winner’s circle at Daytona last year was not an earth-shaking situation; it has long been a widely—and wisely—accepted fact that the Meriden Works twins are capable of some pretty great things. The win, however, was a bit of a surprise, in view of the show of strength by the ever-quick, home-built H-Ds that were favored in the 200-mile climax to the annual Florida speed orgy. Mild-mannered Buddy Elmore, who is, in reality, Superracer, came from deep in the pack at the start and plucked off the front running dicers one by one until the day had become his, and his name was duly entered in the record book. Very little was known about Buddy and his Triumph road racer before Daytona. After Daytona, there was little point in taking a detailed look at Buddy or his machine; the essential story in racing is not the man nor the machine, but the race, itself.
Now, nearly a year later, with last year’s Daytona just so many wonderful memories, and anticipation building for this year’s running of the classic, we find ourselves delving into an analytical look-see at what Triumph will offer for the coming contest. The machine we are about to view, unlike Buddy’s Triumph-Baltimore mount, is owned by Johnson Motors, west coast distributor for Triumph motorcycles in the U. S. The bike, differing little from the east coast version, has been most capably modified and maintained by JoMo’s Dale Martin whose conversance with engineering theory and articulation in presenting the story behind the bike made our task of prying a most pleasant and rewarding experience.
The chassis of the Triumph road racing machine has all standard dimensions. It sports gusseting at the swing arm pivot, which has been incorporated on the ’67 production frames, and additional gusseting on the arms where they tie into the crosspiece. The large-diameter top and down tubes are the same as last year’s frame — another mod incorporated on the production frame for this year.
Hubs and brake components are current Triumph items, and the only non-standard pieces used are the American-made racing linings. The dust cover on the front brake has been windowed to aid cooling and the rear dust cover has been removed to facilitate sprocket changes. In addition, the front brake lever arm has been lengthened for better mechanical advantage. The hubs are laced into 19-inch alloy rims that are fitted with a triangular section Dunlop KR-76 road racing tire in front and a K-70 Gold Seal in back. Martin plans to experiment with a KR-76, mounted on a WM3 rim, for the rear; the triangular section tire on the current WM2 rim has too abrupt a transition from the straight-up to the heeled-over position.
The 500cc T100R engine incorporates numerous modifications, but most of them have been made in the interest of longevity rather than power. The cast-iron cylinders have been overbored the AMA-allowed .040 inch and fitted with replacement pistons which are sand cast and slightly heavier than the original permanent-mold ones. The standard crank and rods were polished and the rotating and reciprocating masses were then rebalanced to Triumph’s standard 70-percent factor. The timing side main bearing and the rod bearings are standard. A singlelip roller bearing has been fitted to the drive side of the crank to permit crankcase pressure pulses to be transferred into the primary case, where they are damped by the additional volume. Three 1/16-inch holes were drilled through the wall separating the primary drive chamber from the crank chamber, and maintain proper oil level in the primary chamber by returning excess oil to the crank chamber, where it is picked up by the scavenge. This modification does away with the timed breather (whose purpose is to damp the pressure pulses), and the engine now employs an atmospheric breather. The lubrication system has been further improved through the incorporation of a large-capacity alloy tank (developed by Triumph-Baltimore) and the addition of a Corvair oil cooler mounted on the right side of the front down tube.
CYCLE WORLD ROAD TEST
The cams used in the Daytona road racer are factory racing items mounted in Torrington needle bearings. The cam lobes work against enlarged tappet bases that are accommodated by larger-than-standard bores in the barrels. Vapor oiling of the tappets replaces the pressure feed, and has been found to be completely satisfactory. The timing gears have been drilled and narrowed.
The combustion chamber shape, passed on to the roadster, is hemispherical; however, the road racer has inserted valve seats, while the roadster employs seats that are cast in. The design permits a two-degree reduction of included valve angle which affords a better valve-to-rocker relationship and increased lift and overlap for better cylinder filling. The intake valves are off-the-shelf JoMo items and the exhaust valves are pneumatic. JoMo valve springs, with aluminum collars which have a steeper angle in the keeper groove than the standard ones, and standard push rods are used. The standard rockers, which have been polished, feature adjusters that are shortened and lightened by having the square end ground off and then drilled with a screwdriver slot added, and the lock nut replaced with a connecting rod nut.
Fuel is supplied by two 1-3/16-inch Amal GPs, mounted to rubber sleeves with Bonneville adapters that have their threads turned off. The carburetors share a single-point-suspended float chamber and employ standard Amal intake bells.
Ignition is provided by a standard energy-transfer rotor-stator combination with the stator encapsulated in plastic. The alternator lead exits from the front of the engine, and a Lucas contact breaker assembly, which runs on its own bearings, is mounted on the right engine cover.
The transmission, like much of the machine, is made up of available Triumph parts. Basically, only two modifications have been made to the assembly; the countershaft sleeve bushing on the mainshaft has been shortened and the sleeve is mounted on a roller bearing. The kick starter mechanism has been removed and the hole in the cover plugged. The rest is all standard, including the shifting quadrant which produces a shift pattern that is the reverse of Triumph’s with the shifting lever turned 180 degrees. The stock clutch (58-tooth wheel) is fitted with steel plates and JoMo’s relined friction plates and is connected to the 26-tooth engine sprocket with a standard primary chain with a riveted master link.
The short, fat fuel tank is something else. This item, manufactured by Triumph’s sister company for production road racers, severely hampers movement of the rider’s forearms and is about as handy as riding with an overinflated beach ball in one’s lap. In addition, the tank ends about eight inches forward of the seat — a needless space that could very easily accommodate the volume of fuel that makes the current tank so fat. The matter is clearly a case of an interim solution and we presume Triumph will see fit to design another vessel for this chassis.
The handling characteristics of the Daytona road racer are quite good — perhaps not as good as a couple of other “legendary” production road racers — but the machine is responsive and handles confidently. Chassis flexing is nil and cornering line is constant and predictable. The brakes are good, despite the hard use they see. Braking could be improved, however, as is often the case with production units used for competition, to offer an additional margin for emergency situations or the increased braking activity required by very tight, twisty courses.
Without a doubt, the Triumph is one of the swiftest road racers ever built. Not only does the bike have a most respectable and competitive top epd, but it accelerates hard and comes out of turns like gang-busters. It goes without saying that Triumph is working toward and hoping for a repeat of last year’s Daytona victory. And with this machine as evidence of their abilities and determination, there is little question that Triumph will be keeping everybody honest at the 200-miler. ■
TRIUMPH
ROAD RACER
SPECIFICATIONS
PERFORMANCE
