Loud click from Flywheel area - HELP!

[MrBounce]

I have a problem where I have a loud "Click" from the back plate/flywheel area of my freshly built engine. It does not do it when the flywheel assembly is off, which thankfully rules out clearance issues from block to gearbox. Could it be something to do with the pressure plate bolts being slightly "off"? No bolts are in the flywheel housing other than those holding it to the block and none of these are pronounced enough to foul on anything. Flywheel has been off 3 times now and I cannot figure out what's causing it. It is driving me nuts!

Engine is A+ 1293, pre-verto flywheel with A+ transfer gears. Flywheel housing is also A+. What is going on???

I have provided a you tube link so you can see (and hear) my issue:

https://www.youtube.com/watch?v=6a3yzkgb-Ic

[Rich]

That's weird, it sounds almost as though something is winding up when you turn the crank and is released causing the knock.

[MrBounce]

I think it's a problem with the drop gears - I will know more when I get the flywheel housing off. I am guessing something is not meshing as it should...