Just a quick tip that could have saved me some time. If u remove the head or cam sprocket for any reason theres a little latch that activates and holds the chain tensioner in place.

In the front of the head u will see a square cut out section that's a guide for a tool to be slid down and release the pressure on the latch as found in the workshop manual.

Go down to bunnings and buy some 6.3 mm wire. Fits perfectly. U will hit the latch and it moves about a centimeter when pushed down. U can let it go as it will stay holding the latch down.

Using a screwdriver, insert it into the cam sprocket and into the cam. Lift The sprocket up and onto the cam. Remove the 6.3 mm wire.