<VV> fuel problem

[GB]

Hello,

A new problem with 65 110PG.

Seems like fuel problem, as it appears to be running on half an engine.
Took off linkage between two carbs, found left side strong, right side 
barely
working.  Overhauled right carb.  Reinstalled, ran like a dream, 
balanced carbs.
Turned off for 30 minutes,  went to take a ride, and would barely start.
Ran very badly, seems like original problem is back.

Maybe garabage in fuel, only affecting one carb?

Thanks for any advice.

Glen