A British Standard exists for motorcycle tyre repairs BSAU 159F, which determines the strength of the repair and where it can and can’t be made in the tyre. Being a British Standard, it is a RECOMMENDATION only, and not the law.
BSAU 159F states that no repairs are allowed in the sidewalls (these flex continuously and a repair is likely to fail) and the standard says repairs ARE NOT ALLOWED on high speed Z-rated tyres.
It says a tyre must be inspected by an expert for secondary damage, run-flat damage, exposed cords and so on.
Michelin is the only manufacturer that recommends that it’s Z-rated tyres can be repaired in accordance with the previous BSAU 159E.
Repairs can only be made in the centre of the tread area, to within 25% of each side of the centre line.
Only two repairs per tyre are allowed up to the J (62mph) speed rating, and one up to the V (over 130mph with 155mph maximum) speed rating. Up to the J Rating, repairs no bigger than 6mm are allowed, and up to V Rating only 3mm is allowed.
All repairs MUST be carried out with a mushroom type plug, which fits into the puncture hole from the outside and bonds with the tyre by vulcanization.
Anything else and the BS says the tyre must be discarded.