11/30/2022 0 Comments Dating a norton dominatorThe cast in carburettor manifold was soon replaced by an alloy bolt on unit. The top speed of the new bike was 92 mph, which was quite good for the day, along with a fuel consumption figure of over 50 mpg even if driven hard. The machine was first seen at the 1948 Earls Court Show and given the designation Dominator Model 7. Ignition was courtesy of the ubiquitous Joe Lucas magneto. The cylinder head was of cast iron with an integral single carburettor manifold and equipped with a 1" Type 76 Amal carburettor. Both inlet and exhaust valves were of the same size at 1.29", compression ratio was 6.7:1. The original capacity of 497cc was achieved by a bore and stroke of 66 x 72.6mm. Old machine tools and old ideas stopped him from producing a one piece crankshaft so a strong three part one was designed with careful attention to detail so as not to copy the Triumph crank. The former was overcome on the new engine by incorporating splayed exhaust ports so allowing more air flow over the particularly hot areas, while the rattling was supposedly reduced by the use of a single camshaft driven by a chain. I hope in these few notes to cover part of the history of the Norton marque, but this time only dealing with the twin cylinder engine and its production changes.īert Hopwood left Triumph in 1947 in order to join Norton as Chief Designer and the opportunity to design his own vertical twin engine without the drawbacks of the Triumph, i.e. in production forms, A third place in the 1961 Senior TT, first in the 1973 Formula 750 TT and 139 mph as a dragster are just some of the feats this engine has achieved and it has also been the basis of some twenty models of Norton through to the last Commando. The basic span of the humble 500cc to 828cc Norton twin engine design was from 1947 to 1976.
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