I know, sounds dumb, it is a big slotted head. Trouble is it is too tight, I didn't tighten it before.
I have tried several things, including grinding on a big screw driver to fit better, and deep creep penetrant. Any ideas? I could keep going at it, and really gum up the head. Thanks

 

Well, I am having same problem with 1977. I heard to get tire iron, not to beat it, as I wanted to, but the end can be shaped to fit and use wrench to twist. Then I am buying a replacement with a hex bolt top. I can not figure why this design.

 

...large screwdriver, width and thickness of slot, apply wrench or vicegrips to screwdriver and it should break free.
Later

 

tried the screw driver and wrench, have to see if my tire iron would be a good fit. May see if there is a slotted head for socket wrenches, used to have one but it grew legs.

 

There is a special socket its is call a drag link, look like a socket with a large screwdriver on it. Its is available at Sears or other place that sells tools. Get one and it will make the removal a piece of cake.

 

Well, I guess I will head to Sears to see/feel for the drag link. I can not find a screw driver that will work, none wide enough.

 

my question mine is even worse what the heck is a
tappet screen

 

Sears website has them, looks promising, will pick on up today locally.

 

STILL WANT TO KNOW WHAT A TAPPET SCREEN IS????

 

the tappet screen is a fine screen that captures any foreign objects. It is located on my bike on the right side of the block, the plug threads straight down. Part of the oil change routine, clean the screen.