Did we agree on which hole it was? :mrgreen:
If its a tinware one, then fit the lead clips or stick a gromit in there.
If its the hole on the manifold joint, thats the adjustment space ... its not a problem.
If theres an actual hole in the pipe itself that we can't see, either replace the pipe, take it off and get it welded, or as BJ1 says, block it off somehow.
To remove the pipe with the engine in place, you'll need to remove the carb and the alternator/dynamo which involves some fan housing jiggling, but its all possible.