Hello John,
Article from Wikipedia :
"Matchless made a 600cc version of the G80 called Typhoon from 1959 to 1962. The engine prefix code was TCS on these bikes. The bore was increased to 89mm while the stroke was increased from 85.5mm to a whopping 96mm. Based on the number of currently known TCS's on the Typhoon register kept by Rick Mann it is now estimated that 225 to 300 were made by the factory over a four year period and almost all of them were sold in the US. The rarest of these is the single down tube framed version, the 1959 G80TCS, and it's even rarer identical sister the 1959 AJS 18TCS. This one year only variant with a slightly smaller cylinder capacity, had a frame that when thrashed was less robust than the models that followed. Nevertheless, it is often favored over the duplex framed TCS models (1960 to 1962) because of its lighter weight and easier maneuverability. There was a road model with lights and a competition model without lights."
Some years ago I've modified a G80CS engine onto a Typhoon, with a rebored barrel to 90mm (to fit a G50 piston, a new crankshaft with a G50 conrod (to keep the hight of the original G80CS cylinder)
All the best - Jean-Paul from France