Just to help out ....
checked my valves and ran into the this issue with the lower timing plug on the left side being SO big
its a 14mm or aprox 9/16"
I didn't have a hex key that big so here ya go
go to your local Ace hardware and get a 3/8"x2:" (or whatever length) hex head bolt and 2 nuts,
the head size of the bolt is 9/16" and with the 2 nuts you have rigged up a way to unscrew that timing cap plug