Posted July 27, 2015
In keeping with the theme started two weeks ago with the Garbage Can Special (see the page “WY. The Garbage Can Special”), this week’s story describes two other garage-built racing motor cycles. Again I apologize for the quality of the images, but the original photos are long lost. These are scans of half-tone images from the yellowed pages of the old Lap Times.
This first article is a modified version of one that appeared in the August 1976 issue of the Lap Times.
The BSO Racer co-authored by Ken Mullins
By 1975 Vance Breese was already a veteran racer. Vance had a habit of racing, um, unusual motorcycles. He once told a story about racing a Bultaco Metralla, crashing into the desert at high speed at Willow Springs. He slid under a pickup truck while the Metralla flew over the truck, or maybe it was the other way around. In 1975 Vance had won the 500 G.P. class riding a BSA Victor 441 (perhaps bored out to 500cc), and had earned the number 5 in the AFM. In 1976 Vance was defending his title in the 500cc G.P. class with a BSO.
What’s a BSO? A reasonable question. You start with a BSA Victor 441. The 441 was called a street-scrambler back in the day, what we now call a dual-purpose bike. Vance took out the 441cc single-cylinder motor, modified the frame a bit, and put in a 498cc ESO motor. The ESO is also a 4-stroke single, but intended for a speedway bike. Speedway bikes don’t have gears, and the ESO motor had no gearbox, so a Norton 5-speed gearbox was added. None of these things were ever meant to work together but on Vance’s bike they all looked natural. The BSO used a Norton fuel tank and sometimes a half-fairing, both painted gloss black.
Ceriani forks and a big 4-leading-shoe drum brake were fitted on the front end. The tires were treaded racing tires, a Dunlop front and a Michelin rear. An exhaust pipe and megaphone were fabricated by Williams Pipes in Redwood City, and Selby Motors helped some. The bike was making somewhere near 50 horsepower at the rear wheel. Vance had considered getting a newer 4-valve head from ESO/Jawa to help increase horsepower.
Some competitors had taken one of the Yamaha TZ750 cylinder pairs and installed them on a TZ350, making it essentially a TZ350 with a 375cc motor. The oversize motor moved the bike from the 350cc class up to the 500cc class. Since the original TZ350 was rated at 60 horsepower, you can see what Vance was up against. Vance used the light weight and good handling of the BSO, along with his own considerable riding skills, to overcome this disadvantage. He successfully defended his title, being the 500 G.P. Class Champion again in 1976.
The following article appeared in the July 1977 issue of the Lap Times. I simply copied the article, so when it says “this year” in means “1977.”
Last year the 50cc GP class was dominated by a neat little Italian bike. The Moto Villa was fast (for a 50cc bike), won a lot, and took its rider to the class championship.
This year things are different. A small yellow bike has shown up and has been winning with regularity. What’s more amazing is that the bike is virtually homemade, a rarity these days of superb factory-built racers. Intrigued by any work-shop built bike, I talked to the owner/builder/rider, Jewel Hendricks. Jewel is a machinist and it’s generally known in the Southern California community that he’s a good one.
The bike is powered by a Dutch-built Kreidler engine. You have to understand about Kreidler – they don’t sell race bikes, they sell motors. Once you talk them into selling you one (Jewel has been at it since 1974) what you do with it is your own business. You get the complete engine in a box, the motor with Kroeber ignition, a silenced expansion chamber exhaust, water pump and radiator, and a handful of counter-shaft sprockets.
A close up view of the motor. The cylinder and head are nearly as big as the crankcase. Inside the cases is a 5-speed gearbox and clutch. Just above and to the left of the motor is the electric water pump.
The engine is a real beauty, a very compact water-cooled single with a 5-speed gearbox. The cylinder is nearly horizontal and is very large for a 50cc bike, giving lots of cooling fluid surrounding the cylinder and head. The motor is nearly square with a 40mm bore and 39.7mm stroke. The bore is plated with “Nickasil,” a nickel-silicon alloy that’s tougher than chrome. Porting is pretty straight-forward with a disk-valved intake. The carb, a 28mm Amal on Jewel’s bike, hangs off the left side of the crankcase.
The engine is rated at a healthy 16 hp at 15,500 rpm. The bike is capable of speeds up to 100 mph, depending on wind and the slickness of the fairing. Remember, this is a production engine; the factory has bikes racing in Europe that have been clocked at 126 mph!
(Left) Everything is tiny inside the engine. The 40mm (about 1.5 inch) piston has a single Dykes-style compression ring. The crank wheels are only three inches in diameter. Also shown are the inlet valve disk and one fiber and one metal clutch plate. (Right) The bore is inside a substantial cylinder with lots of room for cooling fluid.
So it’s a neat little motor, but you can’t win races with just a fast engine. To get through tech inspection you are going to need a frame, wheels, fuel tank, and other accessories. The engine’s shape lends itself to a backbone-style frame, so that’s what Jewel designed and built. The main tube is 1.75 inches in diameter, of .049 inch thick steel. It runs from the top of the steering head straight to the swing-arm pivot tube. There’s a sub-frame that triangulates the steering head then extends rearward to hold the seat and upper shock mounts. There’s a small tube on each side running from the shock mounts to the swing-arm pivot to support the read of the sub-frame and provide a place to hand foot pegs and controls.
At the front Jewel has fitted Ceriani forks stolen from a small dirt bike that he shortened 3 inches and re-valved. The shocks are S&W units that were intended for a minibike that have also been reworked.
One advantage of building you own frame is you can make it fit, and Jewel’s 5’ 9” frame slips right into the bike. It has a longish wheelbase at 51” – by comparison a TA125 Yamaha has a 48” wheelbase. After studying frame theory and asking a lot of questions Jewel selected a 27 degree steering head angle.
“I found that it’s hard to go wrong with an angle of 27 degrees,” he says. He also selected a trail value that, by theory, would give a dead neutral handling. Jewel is pretty happy with the results, but admits that if he did it over again he’d give it one more degree of rake to increase straight-line stability at speed.
The bike’s brakes are single disks at both ends with Grimeca master cylinder and calipers. Jewel made his own disks of aluminum then had them plasma-coated by Harry Hunt. Jewel considered leaving them uncoated but thought better of it.
“They’ll work fine, but if you get one little pebble caught in the brakes the disks are ruined.” The brakes stop the bike through tiny Dunlop racing tires – a 2.00×18 front and a 2.50×18 rear, laced up to “smaller than WM-0” rims. To mount the front Grimeca caliper tabs were welding to one of the fork sliders, then the slider was straightened to remove the distortion cause by the welding heat.
The whole bike works very well. In six races this year Jewel has 4 firsts and 2 second place finishes. The bike has given no real problems, although the clutch plates need frequent replacement and it’s hard to keep the temperature up in the short club races.
The bike is as fast as is claimed. At Riverside recently a rider of a 125 Production bike, who almost never gets passed by a 50cc GP bike, had Jewel pass her coming out of the fast turn 9 (the AFM lightweight race includes both classes). She tucked in behind hoping to get a draft up the front straight when she heard the little yellow bike shift into 5th and leave her rapidly behind. The Kreidler-powered bike was running over 85 mph and still had a gear to go.