Hi again,
I got in a few minutes on the bike tonight and........

I set the timing anew (with the right hand mark) by removing the timing chain tensioner, lifting the chain and moving the gearwheel around so that the timing marks are all correctly aligned (screwdriver indicates TDC as well) and then replacing the tensioner. So far, so good.

Then I tried turning the engine over by hand with the kickstart (which moves freely through its full range now) to check that the engine is freely turning with the rocker cover removed. I noticed that turning the kickstart did not always turn the camshaft which would mean that the timing was "dis-connected" from the engine rotations. i.e. the first time this happened the timing would definitely be out of sync.
I then tried turning the crank with a wrench at the opening in the left hand crankcase cover. Again I noticed that rotating the crankshaft in either direction did not rotate the camshaft, ever. In other words the two are able to move independantly of each other!!

This tells me that the timing chain is not mounted on the driving gear at the bottom OR what else? I can't think of anything else!

While I dismantled the engine I did wonder now and again what system there is to keep the timing chain correctly aligned at the bottom while it is very loose at the top (the manual simply says to tie it out of the way and not to let it drop back into the engine - there is nothing to say that the chain must be kept taut, and it wasn't).

What views on this please?

Dave

ps the timing chain appears to be tight enough on the top gearwheel - no chance of "slipping" for instance.

__________________
Dave