Welcome Ian !
Starting with a manufacture date of 09/80, for the ‘81 model year a lot of changes to the R65 were made .
Lightened flywheel and clutch carrier, crude electronic ignition system is has centrifugal flyweights for ignition advance , aftermarket upgraded systems are available.
Early ‘81’s had ATE twin front calipers, at least for the North American version bikes,after they ran out of ATE’s, Brembos were used .
The ATE calipers had chrome plated steel pistons and are prone to being rusted aftermarket stainless pistons are available, if the calipers are reusable .
The OEM brake pads are very poor in wet conditions, superior aftermarket pads are available .
Charging system is not up to the task it’s been assigned, if you do a lot of city use .
Upgraded charging systems are available aftermarket .
The air box is cast metal, with the air filter and plastic air horns.
The ‘81 model year had problems with excessive valve recession, the valve seats were of a new alloy and didn’t transfer heat from the valve to the cylinder head, but after 43 years I don’t know if this will be an issue anymore, unless you get a real low use bike .
I’m currently riding an ‘82LS after my oil head quit last July, it’s my daily rider to work, I live in Phoenix and ride all year long .
After you get the issues you’re going to find with a vehicle that’s over 40 years old, it’s a dependable bike .