I am confident that I have now got the timing correct but I will let you judge before I put on the valve cover plate or whatever the correct name for the top plate is. It is now also possible to confirm the TDC position with a small rod inserted through the spark plug hole.

As long as your cam chain tensioner is installed, all chain slack taken up, and your marks line up as you show in your pictures, it's good.  You must be able to rotate the engine three or four turns, stop at the TDC mark, and observe all the marks in alignment as shown.

OK, the new chain tensioner is basically in place but I haven't torqued the screws or release the spring and plunger yet. The cam sprocket is torqued but I have not bent up the wings on the locking washer yet.

About the torque specs. The Clymer manual states two widely different forces for the two scres involved. The one accessible from the outside  of the engine holding the upper end of the "tensioner rail" and the one attaching the plunger to the lower end.

It's time to fasten the cam chain sprocket on the crank shaft but what is the best way to lock the crank shaft? Since the nut is left hand threaded I assume I can not use the hex bolt on the opposite side to apply counter force since that might make that bolt come loose?

Should I try and lodge something fairly soft between the gears again?

I managed to flatten a copper pipe and used that to lock the gears so I could start to fasten the nut but I got a bit unsure of the torque specs for that nut so I will check with you guys first. At first I thought the nut sitting in front of the cam chain sprocket was the "crank shaft left-hand flywheel nut" since it is left hand threaded but it wasn't reasonable to torque that to 140-160Nm so when double checking the exploded views and torque specs in the Clymer manual I now suspect that nut is the "primary drive gear nut" specced at 90-110 Nm which looks better but still very high. Should I really use close to 100 Nm to that 30mm left hand threaded nut?

You are correct. It is the primary drive gear nut. 90-110 NM.

Today I finally torqued the clutch nut, the primary drive gear nut and the clutch plate. I also changed the oil filter and prepared everything I could think of before it is time to put on the left and right side cover on the engine but before I do that I would appreciate if you could tell me if there are any last things I should check before putting everything back together? Are there any springs, washers or anything that most people get wrong the first time? I know of the washer that fits on both starter motor axle and the gears that connects to the flywheel assembly but are there any other things?

I have removed the clip to release the new cam chain tensioner. I have bent up one side of the washer behind the clutch nut to keep it from coming loose. I have torqued all screws to the correct specification as best I can.