Might be 1980 model if it would of have a alloy bash plate, although its a little hard to tell, can a you post a decent side on photo showing frame rails under engine? The left side pic looks like there could be the extra frame rails instead of bash plate so could be a 81, but it almost looks like the rail could be owner added and not original too because it looks a little 'iffy' where the rail is attached under the footpeg and not like my frame, but it could just be the the photo giving it that impression too. The decals on side covers seem to look like 1980 from my angle. If the 400 is yellow then they are 1980 decals.
Chain guide is 81
If the tank is 7L its TS185, if its 10L its TS250. Tank is most likely 82 due to the decals
If you want to be 100% sure just email Mick Hone Suzuki with the numbers and they will confirm either 80/81. The PE's are normally pretty easy to ID just by a few features alone but with other suzukis, it always pays to check with an AU dealer because the online number sheets are for USA market and do not match what we have here. The online sheets say one of my TS250's is a 78 but when i checked with Australian dealer it turned out to be a 77, i also found a chart with Au numbers too which also confirmed it.