I did a bit of work trying to get to the bottom of the misfiring. It only happens when I the throttle is close to fully depressed. I checked the spark plugs and have three white and one is black (No.3) but not badly covered in carbon. Do the white plugs indicate too lean a mixture? I have opened the mixture screw about 5 turns so it's not that. Back in at 3.5 turns now. I have checked the timing and replaced the fuel filter. I have a visible 'line' through the middle of the fuel pump (it's hard to see on a photo'. Could it be water or is air more common? I disconnected the engine end of the filter and 'bled' it but couldn't get the air/water/line to go away.
No.3 piston seems to be firing at TDC. I still have not gotten around to replacing the choke pull down unit but I assume that only comes into play when starting and not when up to temp? When I'm paying for shipping from BW what else should I get? I'm thinking a fuel pump pushrod and maybe a new set of leads (although they seem pretty new)? I'm using a DF dizzy with a 2E3 but the vac advance seems to be working fine. I have two other fuel pumps I could try out.
Here are the photos of 1, 2, 3, 4 in order. I have switched 3 and 4 around to see if the 'new' No 3 plug goes black. All cylinders are compression testing at 8.5 Bar except 3 which is at just over 8 Bar.
Any thoughts or suggestions would be much appreciated.