Update on boiler. Got there this am with new capacitor. On arrival noticed lock out on..Odd considering I had switched off at wall and at boiler and told client not to use boiler.. Different story..
Re-cleaned the now oil wet combustion chamber..*?@*%
Removed burner and removed fan and cleaned loosened air band and cleaned. Found small stone jammed in back of band preventing it closing fully. So when I thought I had closed air band there was actually gap at the back. TOO much air... So with that sorted . I replaced nozzle thanks to Kris's Myson performance data sheet, and set pressure. Done smoke test at low air and adjusted down to 2 smoke. Then fine tuned with FGA. Ended with 11.2 co2, 37% excess air, flue temp 277 C, 70 co ppm. any more air to bring co2 down a bit then co ppm rises. Not sure what the recommended co2 is for that boiler.
Anyway happier with that. All that headache from a 2mm stone..
Must say the air band is very fine movements to tune in. I ended up at just under 1 on the settings.