The rings are designed to be bigger then the cylinder. you have to sqeeze them in as you insert them into the bore. (there should be a little guide pin in the ring channel where the the two ends of each ring should meet}
P.s. ideally should only take out cylinder when installing new rings.
I wouldnt, the rings hold the piston away from the wall of the cylinder as well as provide a seal for compression. With only one ring the piston is going to "slap" against the cylinder wall, possibly scratching it, then scratched even with both rings installed your compression will be low because it is escaping by the rings thru the scratches.....
I wood tend to agree with Misteright1 99, although fun story - when i was just a wee lad of bout 11 my old peice of crap motorbike that my folks got me the prevous Xmas ( it must have had at least 10 owners before me and predated the vietnam war), seized. Dad was busy so i went at it - took off the head and looked in side and saw this metal thing stuck between cyclinder and chamber so got out the pliers gave it a big tug, put the head back on and off i went for about another year nd half.... ha ha....wont say it had much power thou .. although at the time iwas told it was the carbs
The rings have nothing to do with holding the piston away from the cylinder. The rings hold compression from getting into the crankcase. The oil keeps parts from touching. There are a lot of two strokes that only have one ring, I have one of the happy time engines that I have with only one ring on the piston, it is more for racing but it is OK for these. The wide double rings on these engines indicates a simple durable engine. You can install the piston in the barrel first leaving just enough out the bottom to slip the pin in, make sure the clip is in the slot to hold the pin in. Have fun, Dave