coil specs

[bradshaw106]

Im going to buy a new coil for my xs. Im getting conflicting info about primary resistance. anywhere from 3.3, 5 and up to 6 ohms.... what is recommended for factory electronic ignition?? the coil im looking at is 5 ohm.
thanks

 

[inxs]

- the original coil for an SG-TCI is an Hitachi/CM12-08A
- 2.5 ohms +/- 10 percent @ 20°C...primary winding resistance
- 13k ohms +/- 20 percent @ 20°C...secondary winding resistance

 

[bradshaw106]

what is the down side to changing the primary resistance??

 

[inxs]

- the way i understand it...high primary resistance reduces current (Ohm's law), meaning coil saturation will be lower than normal...and may not produce enough secondary voltage to fire the plugs under load ... misfiring can occur
- biggest problems with the primary circuit are power input (from battery) and switching (points or transistor)...if not cleanly switched the coil magnetic field wont collapse rapidly and the 2° voltage may not rise high enough fast enough