The Bsa Baja Gold Star
THE BSA BAJA GOLD STAR
Turning An Antiquated Thumper Into The Hot Setup For Baja
Jody Nicholas
THE INTRODUCTION of the BSA Gold Star came in 1938, the year after racing man Walter Handlapped the famous Brooklands (England) track at over 100 mph on his BSA Empire Star and won a “gold star” as the prize.
The Gold Star continued as the mainstay of BSA’s racing machine production until 1963, and Gold Stars could be purchased in many configurations and stages of tune for different types of competitive events. They were successful in English trials, scrambles and road racing in Europe. In America their wins were mostly in scrambles, TT, flat track and road racing events.
In 1963, the Gold Star was available in the United States in three configurations. The Clubman was a sports roadster which featured a race-tuned engine with a U/2-in. bore Amal G.P. carburetor and a silencer to make it legal for road use. The Catalina scrambles machine was delivered with no lighting equipment, scrambles cams and a straight through exhaust system, ready to race right out of the crate. And the most successful AMA racer was the rigidframed Dirt Track model which has left its mark on AMA flat track racing.
Because of its high cost and the growing popularity of twin-cylinder machines, the Gold Star was dropped from the BSA line at the end of 1963. Its disappearance brought sorrow to those of us who fancy single-cylinder machines, both for racing and for pleasure riding.
There are still many Gold Stars in daily use, however, and one of the most enthusiastic groups of Gold Star owners centers itself around Jim Hunter Motorcycle Repair in La Habra, Calif. They do it to get parts and repairs on their beloved “Goldies,” to say nothing of eeting there for cow trailing sessions nd leaving for long trips through Baja California.
I began my AMA professional racing career on a Gold Star which belonged to Joe DiSimone of Devon, Penn., back in 1960 and raced them with success for BSA, Inc. until 1964 and the introduction of the BSA A50 500cc Twin. My neighbor Jerry Marcell (now a development engineer at Kawasaki’s R&D facility in Santa Ana, Calif.) raced BSA Twins in the ’50s and sponsored Blackie Bruce at Ascot on a Gold Star in 1967. We each kept our Gold Stars and turned them into cow trailers and Baja machines, but they were in the standard BSA frames and weighed in the neighborhood of 350 lb., fueled and ready to ride.
Riding today’s potent, lightweight, fine handling dirt machines emphasized just how outdated our Gold Stars really ere. Together we decided to update our machines to improve the handling qualities and lower the weight, yet retain the lusty pulling power and reliability of the four-stroke Singles.
Since the engines are dead reliable and little can be done to improve them for our use in the way of reducing weight, it was decided to begin with a new frame made from 4130 chrome moly tubing. Jerry designed the new frame with twin downtubes like the standard frame, but with the inclusion of an oil tank in the area of the main backbone with the bottom running where the horizontal toptube would normally be placed. The result is a tank which holds 3 qt. of oil and is impervious to damage because of its location beneath the gasoline tank.
The standard steering head angle of 29 degrees was retained, but the engine and transmission have been placed farther rearward and the swinging arm has been lengthened slightly. All frame construction was done by C&J Precision Products in Santa Ana, who manufacture Baker Racing Frames and who built the special frames for the Kawasaki motocross machines. Steve Jentges and Jeff Cole have been building racing cars for a number of years and they worked closely with us fabricating the frames.
We opted for a rectangular section swinging arm because it is the strongest design for its weight, and this is mounted on no-maintenance Husqvarna rubber swinging arm bushings. Timken tapered roller bearings are used at the steering head and these employ rubber seals to retard the entrance of dirt. The complete frames weigh a respectable 27 lb., complete with swinging arm.
We both favor disc brakes because they are impervious to water and are reasonably light in weight, even with the associated lines and master cylinders. Jerry used Harley-Davidson racing wheel hubs laced to Akront aluminum alloy rims. The front wheel has a mount for a sprocket on one side which is now used to attach the front brake disc. The rear wheel is a double-sided affair which allows the mounting of a sprocket on the one side and the rear brake disc on the other.
I decided that as long as these were going to be specials, I’d go all the way. A set of Monotrack magnesium alloy wheels and disc brake calipers were installed. These wheels are more resistant to flexing than conventional spoked wheels, but the rim area is more difficult to straighten if bent, and there is a possibility of the wheels’ cracking if a really hard object is struck when running very low tire pressures.
The engines have been set up neariy the same as those in the Catalina scrambles models using the scrambles cams, but the compression ratio has been lowered to the neighborhood of 8:1 and the ignition timing retarded to 34 degrees btdc because of the low octane fuel available in Baja California.
The abundance of dust found on the dirt roads in Baja makes it essential to have a good air cleaner. K&N air filters like those used on the Harley-Davidson XR racing machines are installed in still air boxes under the seats. Jerry and Steve Jentges from C&J Precision Products fabricated one from aluminum for Jerry’s machine, and Dick Kilgroe of Fibercraft made a mold from Jerry’s airbox and made one out of impact resistant fiberglass for my machine.
Such an arrangement keeps the air cleaners from being ripped off by branches, and the rider’s right leg acts as a deflector, keeping some of the dust from being ingested into the air cleaner, so that it stays cleaner longer.
Long rides during the summer at high speeds in high ambient temperatures are common in Baja, so in an effort to keep the engine oil as cool and clean as possible, H&C oil filter/cooler units are fitted. These cast aluminum oil filter housings are finned to dissipate heat and a pleated paper filter element effectively traps dirt that would normally be circulated through the engine. With all its cylinder and cylinder head finning, a Gold Star engine runs fairly cool, but the addition of the H&C oil filter/cooler reduced the oil’s temperature another 15 degrees F.
When the motorcycles were undergoing construction it was decided to have the frames nickel plated to improve their appearance and make them easier to clean. We checked with Ray Morrow at MCM Mfg. and found that it would be practically no trouble to add a coat of chrome plating over the nickel plate. This would give another layer of plating for protection and add to the overall appearance as well. Many items which would normally be painted are chrome plated, making the machines more attractive. MCM Mfg. did all the plating work and supplied spark arrester/muffler units for cow trailing in California and fiberglass packed sport mufflers for use in Baja where spark arresters are not required.
Darkhorse Kolor in Azusa, Calif, painted the small, 2.4-gal. aluminum gasoline tanks used for cow trailing, but the large, 4.2-gal. tanks which are fitted for long rides in Baja have the color pregnated in the fiberglass. Dean ixom, president of Wixom Bros., Inc., made up the large tanks in the shape of older model BSA road machine tanks. The extra gasoline carried in these tanks lessens the chances of running out of fuel between the often long distances between gasoline supplies in Baja. Dean is a Gold Star owner, too!
Special, thickly padded seats fit into a bow in the frame where the rider sits, making it possible to have a lot of padding without having an inordinately high seat. These are long enough to permit baggage to be strapped on behind the rider if necessary.
Suspension is handled by Ceriani front forks providing 6V2 in. of travel, while rear shock absorbers are changed according to the machines’ usage. Curnutt units are fitted for trips to Baja and Koni, Girling or Boge units are installed tfor general cow trailing.
* Riding the comparatively lightweight Singles is really a treat. My machine lost 60 lb. by the use of the new frame and magnesium wheels, and while it’s not the lightest bike around, the weight reduction and modifications to the engine and transmission location and lengthening the wheelbase have made it an ideal machine for traveling in Baja. And it still makes a good cow trailing mount.
With Baja gearing it’s possible to cruise at 60-65 mph without straining the engine, and the long 58.5-in. wheelbase helps keep the machine on an even keel, even when cornering at speed on rough ground. The steering head angle of 29 degrees has proven satisfactory for both cow trailing and riding in Baja, but the tendency of the machine to understeer was changed by modifying the lower triple-clamp to bring the fork legs slightly rearward, making them parallel to the steering head, reducing the rake and increasing the trail slightly.
Many hours of design and construction time and several small design changes kept us busy the better part of the winter, but the end results are more than worth the effort!
Wherever possible, the machines were fitted with the strongest items available to preclude trouble enroute. Stainless steel covered teflon aircraft lines are used for the oil and brake lines. Bash plates are fabricated from 3/8-in. aluminum deck plate to protect the undersides of the engines and frames. Magura ISDT clutch levers with rubber covers to exclude dirt are used as are A&A and Preston Petty Products plastic fenders.
SUPPLIERS
Frame: C&J Precision Products, 3873 So. Main St., Santa Ana, CA 92707.
Magnesium wheels and disc brakes: Monotrack Engineering, 1725 Monrovia Ave., Costa Mesa, CA 92627.
Mufflers/spark arresters: MCM Mfg. Co., 601 So. East St., Anaheim, CA 92805.
Fiberglass gasoline tanks: Wixom Bros., Inc., 1637 E. Burnett St., Long Beach, CA 90806.
BSA parts: Jim Hunter Motorcycle Repair, 1140 So. Cypress St., Unit A, La Habra, CA 90631.
Oil coolers/filters: H&C Engineering, P.O. Box 7831, Independence, OH 44131.
F ¡berglass air box: Fibercraft, 833 W. 17th St., Costa Mesa, CA 92627.
Air filters: K&N Engineering, P.O. Box 1 329, R iverside, CA 92502.
BSA
