California Hot-Rod
While the Ducati 750 Super Sport legend began at Imola and was sustained in Italy through production racing, elsewhere in Europe and in the US the 750 SS was still regarded as quirky and eccentric. It was not widely available and was never seen as a mainstream sporting motorcycle. Given this scenario the racing success the 750 SS achieved in the US was improbable and quite amazing. It started when Cycle magazine executive editor Phil Schilling attended the Imola 200 mile race in 1972. Schilling had a long history as a closet Ducati enthusiast and spent the week prior to race at the factory observing the preparation of the Imola machines. At the time Cycle magazine was the largest circulation motorcycle magazine in the world and immediately after the Imola race Phil asked Bruno de Prato, Ducati’s press officer, to put him down for the first production Imola replica. This took some time to materialise, but in December 1973 a pre-production 750 Super Sport arrived at Cycle magazine’s offices in Westlake Village, California. It was this bike that became the Cycle magazine production racer.
The establishment of a 750cc production racing class in 1975 suited both Neilson and the pre-production 750 Super Sport, and they proved invincible against other 750s. They nicknamed the bike "Overdog" (antonym of “Underdog”), and still running standard carburetors and mufflers was a genuine 140 mph twin. Production racing rules allowed chassis modifications and Schilling installed longer S&W shocks; plasma-sprayed aluminium brake discs, and a WM6 (3.5-inch) rear rim. The cylinder heads were flowed by Jerry Branch who had worked on Neilson’s earlier Harley-Davidson drag bikes, Jeff Bratton prepared the stock crankshaft, but it was the use of a Goodyear slick tyre at Riverside that provided the 750 Super Sport with its biggest advantage. The superior Ducati chassis didn’t flex as much as on the Kawasakis and BMWs and allowed the full utilisation of the higher grip slick tyres. Neilson won the Open Production race, beating Reg Pridmore’s Butler & Smith-sponsored BMW for the first time. Neilson and Schilling’s 1975 racing season was documented in Cycle magazine, and their 750 Super Sport became the best-known, and most significant, racing Ducati outside Italy.
By the end of 1975 Neilson’s 750
SS was almost as fast as the open class Kawasakis, and when the AMA rewrote its
production-racing rules again for 1976, Neilson and Schilling decided to go for
more displacement. The new rules provided for a maximum of 1000cc, standard
carburettor and muffler bodies, and a standard chassis, although strengthening
was allowed. The bikes also had to have a working headlamp and taillight. With
the factory unable or unwilling to supply replacement cylinder heads Neilson
and Schilling decided to go down the hot-rod route, and so “Overdog” became
“The California Hot Rod”. The development of the 750 Super Sport became was a
broad, collaborative exercise, drawing heavily on specialists from the
California hot-rod culture. This expertise proved superior to that available
from the factory, and the “California Hot-Rod” was undoubtedly the fastest
bevel-drive twin built until that time.
Calculations by Jerry Branch indicated the standard cylinder heads could flow more air, but not enough to make a 1000 cc engine viable. During 1974 Phil Schilling built a 926cc desmo twin but the engine never performed as well as expected. Branch considered 900cc was the maximum displacement airflow would permit. Without access to alternative desmodromic racing camshafts outside the regular “Imola” variety, Schilling decided to stay close to the 750cc for which the camshaft was designed. As ring seal was a problem on the earlier big-bore Ducati, they also decided to use proven components from the Yamaha XT500 single and have Venolia pistons made, with lightened Toyota wrist pins. They chose an 87mm bore, giving 883cc with the standard crankshaft. Branch reworked the cylinder heads with 42mm XR Harley-Davidson inlet valves, and 38mm BMW exhaust valves. A factory oil cooler kit was ordered, but as this didn’t eventuate they manufactured their own out of Volkswagen parts. Instead of standard Conti mufflers megaphones were now built using standard muffler shells.
In the 1976 AMA Superbike race at Daytona the Neilson posted the fastest trap speed of 145.2 mph, and finished third behind the Monoshock BMW R90S of Steve McLaughlin and twin-shock BMW of Pridmore. Throughout the 1976 AMA Superbike season Neilson continued to improve, finishing second to Pridmore at the final race at Riverside in California in October. Neilson led for a while but the BMWs passed him by half distance. After briefly regaining the lead Neilson was eventually slowed with oil problems. By this stage Morris magnesium wheels and attention paid to saving weight saw the machine trimmed down to 181kg, 11.4kg lighter than before. The 750 SS would lose another 13kg before the 1977 season, fronting at Daytona weighing only 168kg. A close ratio gearbox was also installed to aid acceleration, and after the special factory gearbox failed, Marvin Webster, known for building gear sets for Indianapolis race cars, was asked to build a more durable transmission for 1977. But it was all very well installing the best components. Getting the desmodromic engine to perform at its peak was always a science, most appreciated by factory mechanics. Although primarily a journalist, Phil Schilling was also an engine builder par excellence, with a unique understanding of how to get a racing engine to perform at its optimum. Without access to factory set-up data, he worked out the correct preload and expansion rates for crankshaft and tower shaft bearings so the bevel gears would mesh perfectly. As Neilson recalls, “All those gears and shafts that had to be shimmed so carefully? Schilling did all that. It's true that the engine went together like a fine watch. Phil was the watchmaker. I've never known a better one.”
By 1977, with increased magazine
commitments, Neilson and Schilling decided to concentrate on winning the
biggest race of the year, the Daytona Superbike race. After three racing
seasons Schilling considered the pre-production 750 Super Sport a little tired
for another major race so they retired the early bike and commandeered
Nielson’s production 1974 750 SS (engine number 075099, frame number 075363).
The cylinder heads went back to Branch. He sank the valve seats, to accommodate
44mm Harley XR inlet valves and 38mm BMW exhaust valves without touching on
overlap. Further port refinement yielded a flow increase of 7 percent. Along
with new 10:1 Venolia pistons there was a new exhaust system with larger
diameter headers and special megaphones developed through dragstrip testing. On
the Axtell dyno motor produced 90.4 horsepower at 8300 rpm. While this was
impressive for a Ducati twin the Yoshimura Kawasaki Z1s had a reputed 120
horsepower and Neilson and Schilling weren’t overly optimistic about their chances.
Fortunately for Neilson and Schilling events conspired to their aid. “Just days before Daytona, Pops Yoshimura's Hollywood facility had a disastrous fire. It badly burned Pops Yoshimura, destroyed the engine dyno and the 120-horsepower engine, and stopped any further bike development before Daytona. Heroically, Fujio Yoshimura assembled another engine, bolted the Kawasaki together, and got to Daytona,” says Schilling. After the monoshock BMWs had stretched the regulations to the limit in 1976 such modifications were no longer allowed, and for 1977 the AMA also adopted a stricter view towards chassis modifications. This was also advantageous to the Ducati as the stock Japanese frames were severely taxed by Superbike horsepower.
Despite their setback, the Yoshimura Kawasaki still posted the fasted speed through the traps in practice at 153 mph. The California Hot Rod was second at 149.5 mph, this year well ahead of the BMWs. Neilson knew that in the 50-mile Superbike race he had to clear away from the Kawasakis to make the most of the Ducati’s cornering advantage. The danger was the Kawasakis could draft past the Ducati at the finish line if they were too close coming out of the final chicane onto the bowl on the final lap. On race day on March 11 Neilson got away to a flying start. By the second lap he found the break he needed, eventually winning from Dave Emde and Wes Cooley by 29 seconds. Neilson’s average speed was 100.982 mph, with the fastest lap at 102.5 mph, fast enough to also win the Daytona Superbike race the following year. “Not bad for a couple of amateurs,” quipped Schilling after the race. It was Ducati’s greatest racing triumph since Imola in 1972, and still their most important Superbike victory ever in America.
Despite an absence of factory support the
company also received unprecedented publicity. After Daytona the factory
supplied Neilson and Schilling with a pair of unfinished 60-degree cylinder
heads along with 905cc cylinders and pistons, but it was too late. They had
achieved what they set out to do, and knew that factory parts alone were no
guarantee to success. The California Hot Rod was as much a victory for Southern
California hot-rod culture as it was for Ducati.
Their success at Daytona did convince Nielson
and Schilling to contest a few more rounds of the 1977 AMA Superbike
Championship. While Nielson and Schilling concentrated on West Coast events at
the next Superbike round at Harrisburg, North Carolina, Kurt Liebmann rode a
Reno Leoni-tuned Super Sport to second place (behind Mike Baldwin’s Leoni Moto
Guzzi Le Mans). Liebmann finished third at Loudon, and for Sears Point,
California in July, Neilson made a return on the California Hot-Rod. This time
he was beaten by Paul Ritter, on a Dale Newton 860cc desmodromic round-case 750
Sport. In an impressive performance Ritter ran off the track twice but still
won with ease. Nielson’s next outing was at Laguna Seca, where he again
finished second (this time to Steve McLaughlin’s Suzuki 750), and his final race
was at Riverside in October. Now making a habit of finishing second, this time
to Wes Cooley on a Kawasaki with Ritter third, it was enough to provide Nielson
with second overall in the 1977 AMA Superbike series. The California Hot-Rod
was subsequently sold to Dale Newton who put the chassis aside and installed
the engine in another set of running gear for his rider Paul Ritter. Ritter
couldn’t replicate Nielson’s success but this wasn’t a reflection on Ritter. By
1978 the Japanese fours were finally handling well and the days of European
twins dominating Superbike racing were numbered, until a decade later when
twins gained water-cooling, four valves per cylinder and electronic fuel
injection.
I have made a mistake describing the tires on the bike. As you can see from the pictures these are not slicks but treaded tires. According to Cook;
When the bike was reorganized for its appearance at Daytona in 1997, there were apparently no 18" slicks available, from anybody. So Glen Newton & Phil rounded up some kind of high-performance treaded tires, which Old Blue wore for that adventure, and still does. I think they're Dunlops, but I'm not certain.
The owner informs me the tires are Dunlop racing KR124 on the front Dunlop racing KR164 on the rear.
Read Phil Schilling's excellent story on the 1997 Daytona demonstration here;
issues.cycleworld.com/19970901/#!/64