The M6 nut is probably down in the crankcases somewhere now as it sits directly above the camchain. Its worthwhile having a good search around the shim buckets and camshaft areas with a magnet just to see if its sitting waiting to jump into the engine when you build it all up ?
You really do need to find it and when you fit it or the replacement, get the threads really clean and plenty of thread lock on them. Check the other one too !
As for the Emission Valves, just make flat alloy plates and sink them in with silicon, then fit the covers with new gaskets, or a bead of silicon around the edge.
You need block the hole on each cover.
I fitted a Liska Metal Idler Gear to my own 1300 about 2 months (2000 miles ago) and could not hear any different noise from the top end once running, but I do now think I can hear something form that area..............not a bad noise..........just different, but am happy to live with that rather than run the Nylon Gear.
There are very mixed opinoins and info on the length of the ZX11 Tensioner Spring recently and wether to cut it or not and they all make sense, but the latest is that if you cut it, it makes the spring stronger, so maybe best to just leave it as is ?
The ZX11 Tensioner has 19 to 21 TOTAL Clicks in its length, so 11 would appear to be half way. Mine was 10 to 11 clicks and has 40,000 miles recorded and the cam chain is within service limit too.
Pete F
UK