Primary resistance of coil both 4.8 ohms.
Swapped the HT leads of No's 2 and 3 over and did around 50 miles. The black sooty plug has now moved No 3, see photos, No 4 on left. So is that indicating that there is something wrong with that particular ht lead?
With No 2 now showing a more normal colour can I now rule out seal or piston/ring as being the cause?