24-07-2020, 03:00 PM
When you say you have replaced the cylinder head, what have you replaced it with? If it's the later Ruby type with 14mm spark plugs and a two bolt fixing for the top water branch then your problem may well be plug oiling and not a rich mixture. The design of this head places the plugs right over the edge of the bore and if there is any wear it can allow oil to foul the plugs. A hotter range of plug, such as a B5HS can help.