The California Carburetor

When the California motorcycle was announced to the public in The Cycling Gazette in January 1902, one of its leading features was described as a "...carburetor that performs its function so well that it does not cause the gas to deposit soot on the spark plug, and that will use gasoline of any quality."

Designed by Roy Marks, it was sufficiently novel to be granted US patent number 710,330 on September 30, 1902. This patent, together with number 710,329 (Explosive Engine for Motor Vehicles), covered all the major features of the California.

The California carburetor

This is not your run-of the-mill carburetor. Like many of the day it worked on the "surface" principle, and was basically a box in which the fuel was allowed to form a vapour that could be mixed with air and fed to the engine. Unlike the European examples as typified by Minerva and De Dion, Mark's carburetor used cotton wicking to draw the fuel up onto a series of shelves to give a larger surface area for evaporation. Note that there is no equivalent of a float chamber. You, the rider, had to open the tap every so often and add fuel to the appropriate level, as judged by the level glass on the front of the tank. Tricky to do while riding! In practice, with fuel consumption claimed to be close to 200 mpg, one fill would keep you going between stops.

Details of the mixing valve

The mixing valve was a cleverly thought-out affair, controlling the amount of air added to the mixture as it left the carburetor for the engine. The throttle valve - covered under the other patent - was a simple rotating barrel just above the inlet valve.

The carburetor carried through virtually unchanged until about 1905, when it was finally replaced by a spray-type instrument. This change was driven in part by the change in the quality of fuel available as motor spirit. Surface-type carburetors required a highly volatile fuel - with a specific gravity near 0.680 - to function correctly, whereas spray-type carburetors could form satisfactory mixtures from far less volatile fuels, which were both less expensive and less dangerous. When these new fuels became the standard, early bikes would no longer function. Some, like my California, were converted to spray carburetors, and others were taken from the road entirely.

Fossil remains...

Copyright Leon Mitchell 1999

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