Aye william,
Check your earths, integraty of the wiring, especially near the encapsulation, the insulation of the wiring cracks and allows moisture in or breaks the copper wire. If just the insulation is fractured, dry out any moisture by resting the coil on your hot water tank for a couple of days, clean the area with brake cleaner, then use Araldite to seal and reinforce the wires where they enter the coil casing.
Test the coil as follows: Warm the coil to ~20 degrees C before testing.
Disconnect spark plug lead.
Disconnect the primary coil wire (orange) at the ignition coil connector.
Measure coil primary resistance using ohmmeter set at R x 1, between the primary terminal (orange wire) and earth. Reading should be between 0.48 - 0.72 ohms.
Measure the secondary resistance using ohmmeter set at R x 100, between the primary terminal (orange wire) and the spark plug lead. Reading should be between 5.20- 7.80 K ohms.
If these readings are OK then it maybe in the alternator, CDI unit or wiring between that the problem lies. First job is to ensure that all your earths are good and the wiring and terminals are sound before replacing 'bits'!
NB: These reading are similar to that for a TT600 coil.
I hope this helps.
My regards, Bill.
