Loose piston?

I've got a brigs opposed piston engine 20.5 hp, It had gas in the oil, a lot of gas in the oil, knowing my way around brigs I rebuilt the carb. But, it seemed like a large amount of gas in the oil so I took the covers off the pistons, they look fine but one of them has play in it! Anyone had experience with this? Should I replace the piston rings? I can post a video if need be, but basically if I put my thumb on the piston and push up is clicks and moves just a hair. Not sure if this is a problem or not. Any input would be appreciated.

So you have a flathead engine,and you removed the cylinder heads...correct. I wouldnt be worried about slight movement,it is normal.Whats not normal is a large difference in movement from cylinder to cylinder...I would button it back up,and put the cheapest oil you have in it,and get it running...once running if the mechaincal noises of the engine are normal.Id just flush the oil out and put new oil in it,and keep an eye on the level,in case the carb starts flooding again...also beware of pulse crankcase fuel pumps....the diaphrams can develope leaks and draw fuel directly into the crankcase....thats very common as the machines get older and our newer blend of fuel just aggaravates the issues.