hi welcome to Miniriders,
is it an electric start ?
if so there is a slotted chrome cap on the top of the l/h side stator cover that needs to be undone and removed.
also undo and remove the centre 10mm headed bolt of the r/h side of the head.
it's just in front of the spark plug here-
the big round cover on the l/h side (opposite side to the 1mm headed bolt) of the head should now be able to be taken off.
now you should be able to check the timing marks.
turn the engine over a little and in through the top hole of the stator cover you will see a couple of lines stamped into the flywheel.
the first one you see will be the F marking, turn it a little more and you'll see a T marking.
if you can get the T mark to sit at the top of the flywheel, in the centre of the hole that could be TDC
now check the Timing mark on the camshaft gear, there will be a dot or arrow stamped into it.
if the engine is at TDC, then the dot/arrow should be facing the front of the head, at 9 o'clock.
if both of the markings line up then that is TDC, and your timing looks good to go.
if the timing mark on the flywheel is lined up, but the marking on the cam gear isn't, it could be 180° out.
so just turn the engine over a full revolution and get the T mark on the flywheel back to the top again.
now check the alignment on the marking on the cam gear to make sure it is a 9 o'clock