[Spridgets] 1275/carb question

[Dave G.]

12CCDAH + twin SU's...
Carbs balanced with good plug color at low revs.
A litlle bit of a stumble or hunting when idling.
But, bring it up to ~3000rpm and, I can hear a sort of 'spitting' noise coming 
from the rear carb...
I'm going to replace the head with a rebuilt one anyway but a suggestion as 
to what's happening would be helpful...
After a week or so, I'm stumped !!

--
Dave G.   KK7SS
'65 MK III Sprite in Richland, WA

If life begins at 50, why am I falling apart ?!