What size thread repair kits in metric will I need for the 1/2" thread in the middle of the fuel tank, the other thread that holds the pull start in place and the thread that holds the automatic choke cover on.
Whoa just a minute there. By this, do you mean the lug in the upper side of the fuel tank, which has a through bolt which screws into the side of the crankcase? If so, yes it has a 1/2" AF head, but bolts and screws are always described by the
thread dimensions and spec. Not by the head size, which has put us at cross-purposes here, I think.
In this case, the original bolt will be 5/16"-18TPI UNC. So an M8x1.25 ISO metric would be the nearest equivalent, and the size of coil insert to use. I would not favour going up to the next common size, M10x1.5, in this location.
