1015 Engine Head Bolt Washers

Just doing a service and valve clearance check on my Z1100A, and noticed a slight oil leak, which looks like it is coming from the copper washers under the head nuts. Can these washers be replaced by just removing one head nut at a time, or will this cause problems with the head gasket possibly blowing later.

Ride safe Doebag

Doebag, first check if the head-nut is loose. The head may have never had a re-tighten procedure carried out. I have seen some finger tight! If it is loose re-tighten all nuts in sequence.
If it is tight, I would undo all bolts (simply just break/ crack them). Remove the offending washer and replace it with a new one, re-tighten all with correct procedure.
Regardz

Garn is a smart fella but I suspect that your head may have been torqued but the copper crush washer used to seal the oil journal underneath is drooling a bit. To fix it, you don't need a new one generally speaking. Get a torch and heat the thing till it is RED HOT. Then dunk it in some cold water. This process is called annealing and it restores the compression and the thing won't leak. Torque it to whatever a "1015" is supposed to be torqued to for the 2nd tightening... like 25 lbs/ft (PLEASE LOOK IN MANUAL AS MY MEMORY IS BAD AND MY KZ1000 MANUAL IS AT THE SHOP).

by "the thing" i believe george is speaking of the washer, not your alum block/head, as red hot would warp them!

however i am no expert, maybe a warped head will not leak (just kidding of course!)