I'm not sure that video differentiates the overlap stroke or power stroke properly. Wouldn't the TDC mark be viewable twice?? Adjusting the valves on the overlap stroke won't help but could hurt.. This is method I use (not written by me):
Common way: The common way it to find TDC on the Firing stroke. The
problem with this is too many folks end up on the Overlap stroke. This
causes endless confusion, people putting straws down plug holes and endless
other tricks that still often leave them on the wrong TDC.
My way: With this method you do not need to remove the spark plug, magneto
cover, skid plate or the TDC bolt in the bottom of the crankcase or the
associated dirt.
Intake valves; Transmission in top gear, rear wheel off the ground (in your case the crank cover bolt off, and in neutral), if you
have a helper one can watch the valves. Rotate the
engine gently with the wheel to locate the point where the exhaust valve
starts to open then rotate very gently until the exhaust valves are 1/2 way
open! Minor frustration, we are now fighting against the valve spring which
wants to roll the engine back, so to stop it you either have to have a
helper hold the rear brake or, as this gets pretty boring so;
Option 1; Take a tie down, hook one end to the brake pedal, wrap in under
the bike and up the left side to something like the top of the frame behind
the engine. Now just tighten the strap so the brake can keep the engine from
rolling back.
Option 2; ( I use this method) Put a bar thru the spoke of the rear wheel adjacent to the swing
arm to stop the wheel.
In your case you should be able to have a helper hold the engine turning nut in positon with that 17MM socket
At this point the Intakes are on Center of the Heal of the Cam. Proceed to
adjust.
Exhaust valves; As above, except, locate the point where the intake valves
have opened and are 1/2 way closed (engine rotating forward). As the intake
is closing the engine will want roll forward PAST the way point and the
lash in the transmission and chain will make it so you can not stop the
engine, so let it go just past, then roll the wheel backwards and secure it
with the brake or bar again. Now proceed to adjust the Exhausts.
ALWAYS! ALL 4 STROKE ENGINES: With the engine rotating its correct direction
the exhaust is adjusted when the intake is closing and the intake is
adjusted when the exhaust is opening!
I'm no mechanic and have never worked on that bike - just trying to make a point that you need to be on the right stroke if you are using the TDC method - might be easier/other options on that bike.