We recently re-built the upper end of my Comet because it was not possible to purchase a new 90.. piston. It is now standard but may have Mk 2 cams but we re-fitted the 32 mm Concentric and she started beautifully and ran well for 8 miles or so and was then impossible to de-throttle. I tried everything and the same thing always happened when she warmed up. I removed the Concentric completely and a machinist friend has informed me that it is junk so I have re-built and fitted a Monobloc. I only have a 230 main jet in it and I am not sure of the others. After some problems with loose pilot jet etc, we have her running fairly nicely but she is now very difficult to start and, even after 8-10 kicks with tickling and full choke, the plug is dry. I am getting great spark but obviously no initial fuel. In looking at "Forty Years On" there is a good article by R. Swannick on tuning the Monobloc for a Comet and he seemed to recommend 280 Main jet, 106 needle and 30 pilot which looks right but may not really solve her getting fuel for starting. When I tickle her, fuel runs out of the bellmouth. With 8-10 kicks on full choke she should then be flooded. I have dropped the needle down one but that should not be my problem. She started so beautifully on the old Concentric, what should I be looking at now with the Monobloc?