2020 1250 RTW Fill Plug?

On the left side of engine, high up, and behind the cylinder about the 0ne o'clock position from the oil filter is a plug? that looks similar to the final drive fill/drain plugs. What is that?

Cam chain tensioner. You will find one similar on the r/h side, straight aft of the oil site glass.

OK Thanks

That's the access plug to insert an 8mm pin that when centered in the access hole engages the rotor of the alternator and will put the pistons at the full out position. Both pistons are full out, or full in at the same time since they are on different crankshaft pins for their connecting rod.

Only one piston at a time is actually at TDC (top dead center) since that is by normal definition the cylinder at the firing point.
The other cylinder is in overlap just at the end of the exhaust stroke and beginning of the intake stroke.

Here is the factory part #83302327796 shown on the bottom and the DIY tool that I make above it.

Cool. So that tool eliminates the old process of finding TDC by rotating the wheel and marking the belt pulley as on a 2002 model?

Ok, I thought you were referring to the one on the cylinder itself. From a recent Boxflyer Wethead Tech Day Demo I learned a little about both, but did not learn enough to know which plug you were talking about. Sorry for the confusion.

Kudos to Boxflyer for staightening things out!