glad i found this on the net before i tried starting the blue bikes motor, looks like ive got a 180 and a 360 crank so will have to find some wirirng diagrams to rewire the green bike to run the other motor (that should have more power-rev better)
"The CB125T, whether early 6v and points or later 12v and CDi ignition, has a 180 degree cranks; one piston up, one piston down. Consequently it needs two seperate ignition circuits, with two seperate ignition coil to provide sparks at the right time. Coil you describe, with two High Tension leads to both spark plugs is possibly from a 360 degree crank engine, that has both pistons rising and falling together, or is a generic 'pattern' replacement. On the 360 crank motors, only one ignition circuit is needed, triggering both spark plgs similteniousely, once per engine revolution. One piston will be aproaching TDC on the compression stroke, with a charge in the pot the spark will ignite; other slug will be rising on the exhaust stroke, with smoke in the pot, and a spark in there wont really do much, so firing plugs to gether saves some hassle. On next cycle, it will be the other way around. Almost all the small honda twins APART from the CB125 have 360 cranks; the engine could be from a CM125 'Custom', a CA125 'Rebel' a CD125 'Benley', could also be a 200 engine from CD or CM, or even 233cc from a CB250 'nighthawk' or CM250 Rebel... So before going any further we need to bottom what you got; becouse I suspect its a mongrel. CM125 motors in CB125's are common swap. They are bolt-for bolt directly interchangeable with the CB engine, as they are bilt on teh same crank cases and use the same barels and heads. The CB's are revvy little things tuned for 13 or 17bhp dependant on guise; the CM's & CD's are sloggers, tuned for reliability & ecconomy making around 10-11bhp at best; they make good donor's becouse they dont tend to be worth as much, and less stressed, they dont get so thrashed to pieces. "