Well Guys, i think i may have found the culprit but have no idea how it got this way. When i took a magnifying glass to the main jet it was clearly stamped 106. So, i have a tray of cvk 24/30 jets in the garage. I picked out a 130 jet but quickly found the actual jet was too big for the housing. After some (not so very precise) measuring i discovered my CVK 30 carb jas CVK 26 jets..I had a CVK 26 120 jet so i fitted it and Viola, no more bogging down. It does pop and bang on the overrun so its still way too lean. Now i have to find the standard jet size for a 250 people and somewhere to buy these jets in CVK 26 sizes....