I removed the backplate and it was clean inside. I couldn't tell if the crankpin is worn but it looks to be a bit irregular. I can see some slop between the pin and the needle bearing but I can also see a little slop between the wristpin/bushing too. The clicking at idle must be the movement (slop)of the connecting rod when under pressure. I can see and feel it move.
I also noticed what seems like excessive slop in the prop driver and the crank. Didn't look like any excessive wear on the crank, driver or key but there's about 2-3mm of slop back and forth . Just seems like there shouldn't be that much.
Here's some pics and there's really not much to see. Will require a tear-down to find out if anything is worn. Looks like I'll put the backplate on and send it in .