smythie,
Did you check the throttle shaft bushes and for wear on the throttle shaft as this could cause air leaks throwing out the mixture. As it has a fixed high speed jet make sure that you have it screwed down correctly.
Also did you replace the pump diaphragms?
We do have a workshop manual that can be uploaded to the parts list and manuals area but it is over 5MB. If you wanted just the carby info uploaded it would be a lot smaller size.