The plug should be an interference fit but shouldn't take too much force to hit the plug in .If you use Loctite which is fuel resistant the plug must be a snug fit otherwise there is an air gap and the Loctite will not cure.
If the hole in the carby is deep enough you could put a 3 mm deep plug in like a bit of a tig alloy welding rod etc and if the plug is just sliding into the hole loosely you can hammer say a 3 mm deep plug on a bit of metal to make it sightly wider ( or slightly squash the plug with Vice Grips) ,you could also file a slight taper into the plug and hit it in .
Even a lump of solder could be hit in if the hole is deep enough. I'd make the plug sit flush as it is originally.
I've made welsh plugs out of old coins to block the brake fluid window on motorbike brake master cylinders and that stops the fluid leaking from the old damaged sight glass.
With the old ignition points line trimmers ,I just remove the Powertorque ignition module and wire it to the kill switch wire on the trimmer.
