[Mg-t] SU Carbs!?!?!

[wbeech at flash.net]

Hello list,
 
Got the SUs cleaned up and replaced a couple of questionable seals.  All
back together, no leaks, jets centered, slides sliding.  Now I am ready to
fine tune and sync them up.  
 
With linkages disconnected I and rev the motor to red line with the front
carb and watch the slide gradually go up until only about 1/4" remains
visible.  However, with the rear it won't rev all the way and the slide will
only go to the halfway mark.  Both slides move up and down freely by hand.
 
Check for air leaks & float levels, all appears to be good trying to do
everything by the book.
 
Any suggestions?
 
Thanks,
Bill