..its a sideport 250 engine with the inlet machined and welded to make it downdraft centre port , the port is now 38mm and the exhaust port is 42mm..with 35mm inlet and 30mm exhaust stainless jawa speedway valves,springs and ti retainers,with combustion chamber altered to suit.
The rockers have been converted to rollers and it has a needle roller cam to suit, it has a carillo rod fitted with a larger 12:1 piston giving a total cc of 298....i've been experimenting with electronic ignitions but will use points until I get it dialed in..
pic of roller rockers with standard ones to compare..