Methanol fuelled Tiger Cub

This is an engine that we built for hill-climb competition in the Channel Islands,and which was required to run on methanol fuel, and thus needed considerable reworking..  The crankshaft was completely rebuilt, and all engine and gearbox bearings were replaced. New valves and guides were fitted, with the rockers being lightened and polished,besides being mounted between bronze spindle spacers to reduce friction. The valve springs are racing Kawasaki items set up to give 75 lbs fitted load ,with the existing steel valve collars being machined to accept the slightly different internal diameter. The inlet tract was gas-flowed and satin-polished, and the inlet valve seating width substantially reduced.The inlet valve head was lightly reduced in diameter,and given a polished,radiused edge.
Tiger Cub 1
Tiger Cub 2
 Careful searching turned up a Hepolite piston that gave an initial compression ratio that measured out at 16:1, but which was reduced to 13.9:1 in order to give the bottom end a slightly easier time of it,and to improve flame-travel. Squish, piston-to-valve,and plug-to-piston clearances were all carefully checked and modified where necessary to take account of the level of flexure estimated to be likely in the crank assembly under arduous usage.  Carburation is by a 600 series Amal Concentric specifically modified for alcohol use,and ignition by a Boyer Micro-Digital system. The machine fired up with no hesitation once the engine and systems were installed by the customer, sounding absolutely superbly crisp , highly responsive, and marvellously crackly. That'll frighten the seagulls....
Tiger Cub 3
Tiger Cub 4

The incorporated engine:

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