Richard,
Removing these studs is not a problem (normally!) Use the two nut system and lock them well together. Then using the nut closest to the head unscrew anti clock. This has the effect of tightning the nut used against it's locker. Don't over torque. If the stud does not move with moderate force, stop. Think again. Do I need to do this.
Carefull
TIP... Put something in / over the inlet ports to block them off prior to any work as soon as you take the carbs off. This prevents any foreign bod's ending up in your engine.
) I just use some masking tape or duct tape. Try that 1st...
When fitting new ones don't thread them all the way in tight. Use a little locktite on pre cleaned studs and threads. Allow this to set. This makes sure you have enough threaded area to properly seat the lock nuts. Min 1.5 threads protruding. Check the manual for the gap on the thackery washers. Don't whack them all the way up. Carbs must 'float' on (I think) 40 thou (1mm) gap on the thakery washers (spelling!)
Alex B....