Funny - I am just about to post my "new member" post and read this one first as I just bought an '82 R65LS as well - after you described a leaking left carb and a high idle of 3-4K I almost thought we bought the same bike!! I will keep following this for fixes for the issues!
Hopefully not the same bike - mine was still there on Sunday when I last looked! Carb leak was the float gasket. Fixed the left and then the right started to leak - noticed on a trip to my local BMW dealer for something else so checked with the parts dept on the price of a float chamber gasket, and they had one on the shelf for £2.41 (from memory). It's probably the cheapest part I've ever bought from a dealer!
As for the intermittent high idle, the choke mechanism on the right hand carb is slightly sticky - as long as don't use the choke or, if I do, I remember to check it's closed properly with my finger, all is good.
