Righ vaccum piston higher than the left K400B 1978

Hi,
I am quite new to the forum. Bought a K400B 1978. When I started to clean the carbs I noticed that one of the vaccum pistons sits higher that the other. Inspected both, no sigh of wear or bend. Is that normal?Does it have something to do with the fact that it is a singe exhaust motorcycle?!
Thank you

They should be at exactly the same height, and should be all the way down when the engine is not running or when the carbs are off the bike. Sounds like something is binding one. Gently push each one up, then let them fall. They should fall smoothly with a clunk when they bottom out. Dried fuel, corrosion, a bent needle, or maybe even a small bat colony could cause one to hang up,