The bike bought by Burt Munro carried engine no. 5OR627 and can therefore be seen to have come very early in the life of a machine which remained in production, in basically the same form until 1931.
The Scout itself was a 37cu.in. (60Occ) 42 degree V twin with side valves. A helical gear primary drive was contained in an oil-tight, cast alloy case and a 3 speed, hand change gearbox with foot clutch was fitted. A double down-tube cradle frame was used, rigid at the rear, and a leaf-spring provided the forks with nearly 2 inches of movement at the front. Chain drive was used in contrast to the drive systems still commonly used on English motorcycles.
Burt began modifying his bike in 1926. His methods, to say the least, were unorthodox. He used an old spoke for a micrometer and cast parts in old tins although one American report has him casting pistons in holes in the sand at the local beach! He built his own four-cam design to replace the standard two-cam system and converted to overhead valves.
He made his own barrels, flywheels, pistons, cams and followers and lubrication system. In their final form he in effect hand-carved his con-rods from a Caterpillar tractor axle, and hardened and tempered them to 143 tons tensile strength. He built a seventeen plate, thousand pound pressure clutch and used a triple chain drive. He experimented with streamlining and, in its final form, the bike was completely enclosed in a streamlined shell. The leaf-sprung fork was dispensed with and what appears to be a girder fork from a 1925 - 1928 Prince substituted.
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