During this time, manufactureres began to realize the advantages of overhead-valve technology for their racing efforts. In 1928, Excelsior jumped in with both feet in orderto produce a factory 45 cubic inch Class A overhead valve hillclimber to compete with Indian’s "Altoona" OHV 45, utilizing a bottom end simliar to the company’s "Super X" road model, and a specially cast, overhead valve top-end with hemispherical combustion chamber and detachable, bolt-on heads. Given the advantages of increased compression capabilities, these machines were set-up to burn alcohol through special aluminum racing carburetors. It is rumored that only 24 were built, two of which are on display at Wheels Through Time. The later of the two machines, is serial number OH103 — the third built — and was ridden to the 1930 National Championship by Gene Rhyne, after a short stint as Joe Petrali’s personal mount during his years with the Chicago-based Excelsior.
Excelsior’s new machine was immediately victorious in many big events, showing Indian they were a force to be reckoned with when it came to OHV technology. Harley-Davidson would not have their 45 cubic inch OHV ready until the middle of the 1929 season.''
After some initial success with the Super X model on the dirt and board tracks during the 1926/27 seasons, Ignaz Schwinn began to show interest in racing for the first time since the death of factory rider Bob Perry in 1920. Sometime in 1928, he instructed chief engineer Arthur Constantine to develop a competitive machine that could capture the National Hillclimb Championship with the right rider aboard. Constantine immediately went to work, relying on a young Chicago native and Excelsior Racing Department engine-builder and tuner named Andy Koslow to finish the task.
They based the bottom-end on the high-performance Super-X, which had been race proven for two years already, but modified the bore and stroke. Special, twin-port, cast-iron, overhead valve top ends were produced, with hemispherical combustion chambers, which provided for much better airflow inside the engine. Compression was out the roof at 14 to 1, and the machine burned alcohol for maximum horsepower. The chassis were specially built for hillblimbing, small tanks, low gearing, and only a single speed in the transmission. Koslow himself test-rode the machines and raced them in many events to some success. He left the real riding, though, to the professional hired guns of Excelsior to reel in the fame. Joe Petrali took home the 1929 National Championship in 1929 and Gene Rhyne took top honors in 1930. Koslow and Constantine had developed America’s top Hillclimb machine.
When Ignaz Schwinn unexpectedly instructed the management to "close the doors" at Excelsior in 1931, just a year off two National Hillclimb Championships, Koslow made sure that his technology was not lost, and convinced Schwinn to allow him to retain the blueprints and molds from the company’s overhead valve endeavors. Over the following years, he would go on to produce a very limited number of specially built OHV motorcycle and midget car engines, and also may have provided parts to other companies. Ever since, these special dual-port cast-iron top-ends have been known as "Koslow heads". In the hillclimb exhibit at WTT, there is an undocument, one-off factory built Harley engine with these very heads on it.''
Build by Jurassic Customs in cooperation with Cheetah Custom Cycles in Japan
It won Jeff Leighton's Pick @ Yokohama Hot Rod Custom Show 2015
Owned by Shinsuke Takizawa
Photo credit Cheetak Custom Cycles / Kentaro Yamada / Roller Mag / Fly Wheels / Hiroshi Nose / Masu / Tsu Kanazawa
Quotes via Wheels Throught Time
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