Velostar Street Scrambler
Engine: Velocette 499cc air-cooled OHV single, 86mm x 86mm bore and stroke, 10:1 compression ratio (8.75:1 stock), 40hp-plus (39hp @ 6,200rpm stock)
Top speed: 100mph (est.)
Carburetion: Single 32mm Amal Concentric
Transmission: 4-speed, chain final drive
Electrics: 12v, solid state BT-H magneto (BT-H racing magneto stock)
Frame/wheelbase: BSA Gold Star dual downtube steel cradle/57.25in (1,454mm)
Suspension: Husqvarna telescopic forks front (BSA telescopic forks stock), dual Öhlins shocks w/adjustable preload rear (dual Girlings stock)
Brakes: 6in (152mm) SLS drum front, 8in (203mm) SLS drum rear
Tires: 90/90 x 21in front, 120/90 x 18in rear
Weight (dry): 320lb (145.5kg)
Seat height: 33in (838mm)
Fuel capacity: 3.5gal (13.25ltr)
Ever since an enterprising mechanic first fastened a stationary engine to a bicycle, motorcycle builders have been mixing and matching engines and chassis. In the early years, it was usually motivated by expediency. Many motorcycle makers — especially in Britain — were small companies that had started out building bicycles. Most could turn out a motorcycle chassis and running gear, but the expertise, equipment and machine tools to produce a motorcycle engine required a significantly larger investment.
As a result, it was not uncommon to find that your Sun, Cotton, Rex, OK-Supreme or even Vincent-HRD was powered by a proprietary engine from Villiers, Blackburne, Rudge or JAP. In fact, the most prestigious bike maker of his day, George Brough, never built an engine of his own, relying on JAP and Matchless to power his Superior motorcycles.
But by the 1950s, the British motorcycle industry had consolidated, and proprietary engine makers all but disappeared — save for the ubiquitous Villiers 2-stroke. Engine swapping now focused on matching the superior handling of, say, the Norton Featherbed frame and the tuning potential of, for example, a Triumph 650cc engine. It’s said the Triton came about as a result of the popularity of Formula 3 auto racing in the early 1950s. Formula 3 limited capacity to 500cc, and the engine of choice was the double overhead cam Norton Manx. Norton refused to sell its engines separately, so engine-less Manx chassis started appearing in the classifieds. The custom building era is older than you might think.
The Velocette engine
The VeloStar’s engine dates from the late 1950s — an MSS 500 type “S” as used in Velocette’s motocross bikes. The MSS has its origins in the 1930s as a derivative of the 250cc MOV and 350cc MAC engines. Velocette had focused on the race-bred overhead cam KSS as its lead model with the prosaic GTP 2-stroke for the commuter market, leaving a gap in the middle of the range. The 1933 MOV was intended as a sporting lightweight to fill that gap, but easier and cheaper to produce than the overhead cam bikes. Thus the specification called for pushrod-operated overhead valves. Velocette did, however, place the camshaft as high as possible in the engine to reduce moving mass in the valve train — leading to the famous “Map of Africa” timing cover shape. The MOV became the template for all Velocette overhead valve singles until production ceased in 1970.
The most popular engine size for a sporting motorcycle in 1930s Britain was 350cc, so the 68mm x 68.25mm bore and stroke MOV begat the 350cc MAC of late 1933, essentially a MOV with a long, 96mm stroke. When dealers requested an even bigger engine (primarily for sidecar duty), the factory responded by increasing the bore to 81mm for the 500cc MSS.
After the end of World War II in 1945, the MSS reappeared as before, but was dropped from the range in 1948 while Velocette concentrated on the new 150cc LE. Meanwhile, the sporting MAC was getting a makeover. For 1951, principal changes included the use of a light alloy “Alfin” cylinder barrel with iron liner, a light alloy cylinder head, and Velocette’s own telescopic fork. In 1953 the MAC got a new frame with an ingenious swingarm rear suspension, which was adjustable by means of sliding top shock mounts.
The MSS was re-introduced in 1954 with the bore and stroke revised to 86mm x 86mm — not because shorter strokes were necessarily better, claimed designer Charles Udall, but because that was the longest stroke they could use and have the engine fit in the new MAC frame! At the same time the MSS got an Alfin cylinder and alloy head. Both the 350 and 500 were relaunched as the Viper and Venom, respectively, in 1954, with the 350 also adopting the 500’s bore of 86mm.
The final specification of the MSS engine used in the VeloStar is as follows: 86mm x 86mm bore and stroke, 499cc, air-cooled, high camshaft overhead valve 4-stroke single with alloy cylinder and head using hairpin valve springs. (Udall claimed the resonant frequency of coil springs could cause valves to float.) The bottom end used a built up crankshaft with a shallow taper fit into the flywheels (to avoid the need for locking nuts) and a single-row roller big end with a duralumin cage.
The camshaft operated quadrant-shaped followers working the rockers via short pushrods. The crankshaft was located in the cases by tapered roller bearings, which were shimmed to a slight preload during assembly to control side play. Drive to the 4-speed gearbox (featuring the sequential foot-change that Velocette invented in the 1920s) was by chain. The MSS retained magneto ignition and Velo’s characteristic belt-driven generator.
The motocross version of the MSS bore the engine number suffix “S” and was mildly tuned with 8.75:1 compression, an Amal TT racing carburetor and a close-ratio gearbox, while missing lighting equipment, battery and the belt-driven generator. The engine went into a frame with a non-adjustable swingarm rear subframe. Eric Cheney raced an MSS in the mid-1950s, but with the engine in a Featherbed-style frame. Cheney still sells a motocross frame kit for the MSS engine.
The BSA frame
As would be appropriate for an industry that had its roots in building bicycles, most British motorcycle frames were made from mild steel tubes brazed into cast iron lugs. Frames made that way tended to be strong, but heavy. By the early 1950s, developments in welding technology meant that frame tubes could be welded directly without lugs. Two of the earliest production frames exploiting this technique were the sif-bronze welded Norton Featherbed developed by Rex McCandless and BSA’s A10/Gold Star swingarm frame produced at the company’s Small Heath factory in Birmingham.
Both frames dispensed with lugs, using triangulation (Norton) and/or gusset plates (BSA) to get the required strength at the steering head and other critical points. Both were acclaimed for their fine handling. The Gold Star frame was almost identical to the A10 frame except for a kink in the right-side bottom rail to fit around the Goldie engine’s oil pump housing. Apart from that, both used similar dimensions and materials.
It’s interesting to note that those who claim to know the subtle differences between the A10 and Gold Star frames are sometimes loath to divulge them. This is because of the large number of fake BSA Rocket Gold Stars that have been built over the years. The iconic Rocket Gold Star used an A10 Super Rocket engine in a Gold Star frame, but without the oil pump kink. Many unscrupulous builders have assembled RGS “replicas” around an A10 Super Rocket engine. And while the performance of a replica may be similar, its value isn’t. Caveat emptor!
Velocette did develop its own special motocross frame for the MSS “S” in 1959 with a new triangulated rear section, and fixed rather than adjustable shock mounts. But the new rear was merely bolted to the existing main frame.
The VeloStar came about as a result of a challenge that originated in Maui, Hawaii, between former AHRMA racers Dave Webster and Laf Young. The challenge: each would build his own motocross “special” for entry in the Premier Heavyweight class at The Farm, AHRMA’s annual off-road round in Chehalis, Washington.
Webster’s plan was to drop a Norton 750 engine into a BSA A10 frame and fit running gear from his collection of late classic dirt bike parts. Young, meanwhile, kept eyeing the Velocette MSS “S” lurking in his shop.
Young bought the Velocette in the early 1970s: “On moving to Oahu in 1970, I started asking around about unusual Brit bikes — particularly a Velo,” Young says. “A shop owner in Kailua remembered seeing a street Velo in Kaneohe.” After moving to Maui in 1971, Young traveled frequently to Oahu, and kept trying to track down the phantom Velo.
“Years later I located it in the garage of a man named Ray Howard,” says Young. “He was in his 90s. He had brought the Velo to the Islands from California in the Sixties. I visited him and got it running. He sold it to me sometime later and I shipped it to Maui and he passed away shortly thereafter.”
In the meantime, Young had bought a BSA frame from Michael Morris in San Francisco, California, as well as an authentic Gold Star seat and a U.K.-made Lyta alloy gas tank. It turned out the frame was a factory-modified Gold Star item that had the kink in the lower right frame rail removed and a straight section welded back in. “So it was a genuine Gold Star frame,” Young says. “I then discovered that a guy named John Ford from the Bay Area had a Dick Mann version of what I was trying to build.” Ford referred Young to Mann himself.
“I called Dick and we spoke at length about the motor mount plate choices, and particularly the countershaft sprocket to swing arm pivot placement.” Young was then able to make new engine plates and modify the existing ones “to shoehorn the Velo into the frame,” he says.
With the frame now ready to accept the engine, Young looked around for parts to complete the VeloStar. “I sourced a set of Husky forks and triple trees from the Seventies and adapted them to the Gold Star frame. I got 9-1/4 inches of controlled travel. And I found a new set of Öhlins (shocks) on eBay. The seller had no minimum price and I was the only interested party. I bought the pair for under $200!”
The quick-detatchable rear hub came from a BSA dirt bike, which Young mated to an 18-inch Excel alloy rim, while the Husqvarna front end rolls on a 21-inch Akront rim. Young also adapted Husqvarna fenders, handlebars and controls to suit. The oil tank is BSA, also.
Meanwhile, the MSS “S” engine was getting a makeover at Dave Smith’s Classic Motorcycles (no longer in business) in Plainfield, Illinois. “I sent the engine to Dave for his perfectionist detail in Velo restoration,” Young says. “We fitted a new piston to raise the compression ratio to 10:1. He added a second sparkplug. He also converted the engine to coil valve springs and changed the cam for more performance.” Young bought a new solid state dual-spark magneto from BTH Components Ltd. in the U.K., and fitted a New Amal Concentric carb and a K&N air cleaner.
Sadly, Webster started experiencing health issues, and the Chehalis challenge lapsed. Though the VeloStar was ready to run, Young lost interest in the project and it sat under a tarp for a few years. Enter Roland Ortiz of Laguna Niguel, California.
Ortiz to the rescue
It was on a family vacation to Maui that Ortiz dropped in on Young — and decided he wanted to buy the VeloStar. Young wasn’t keen at first, but came around to the idea. After all, the project had stalled for some years.
“Roland showed up and we made a quick deal. He applied the spit and polish and added the street gear. It is a beauty to look at,” Young says. “Little by little, I started cleaning up the VeloStar,” Ortiz says. “There was a lot of crud on the bike just from sitting for a long time. I decided I was going to make it street legal.” That meant adding lights, a battery, speedometer and drive, and tin ware.
“It’s an MSS Scrambler engine. It was a Scrambler originally. I have a couple of pictures of when Laf first got it. He was going to run with the original frame, but it was too rigid. That’s when he decided to build the VeloStar.
“I’ve taken it to a couple of shows,” Ortiz says. “People ask me a million questions trying to work out what it is. Then I start telling them, and they say, ‘Wow, the engine looks like it was made for that frame!’”
Although the VeloStar had not run at the time of our photo shoot, Ortiz finally fired up the bike at Willow Springs Raceway in California in May 2016, and he’s pleased with the result. “The engine sounded nice and strong,” he says. Ortiz says he plans to ride the VeloStar on the street, as well: Chances are pretty good he won’t see another one on the road! MC