Honda XR80 '80 US Forum

Hello, Newbie here.
I'm going to put a Heli coil in my 1980 Xr 80 and from what I read it would require a 10x1 heli! I bought the 10x1 heli coil today and here is my concern.
The spark plug which is an ngk C7HSA does not screw into the heli because the heli seems way to big and the plug will just drop into the heli. I tried a 10x1.25 yesterday at Napa and the same ngk plug screwed into it nice and tight.
So did heli package the wrong size or will it get a lot tighter when I install it? Seems like the 10x1 is around a pencil lead too big when installing dry.
Thank you for any help