[Rev]

I had that low rpm cruising stumble once. Since the carb is running almost entirely off of the idle/transition circuit at those low cruising rpms, the idle being set too lean will cause a stumble sometimes under those conditions. How many turns out are your idle mixture screws out from the closed position? I had to richen mine a little more to get rid of the stumble but then it was a little rich at idle. I eventually had to open up the low speed or idle bleeds to get everything just right.

Rev