Not a good idea to weld an aluminum motorcycle frame unless you have the facility to heat treat the entire frame AND assure alignment. The frame was made of aluminum for weight reasons. The strength to weight ratio is only superior in the treated state, as-welded cuts that ratio by at least 3, more likely 4 or more. So if it were 6061 in the T6 state, the yield strength (stress at which permanent deformation happens) is in the 36,000 PSI range, about the same of A36 structural steel. As-welded, the yield strength is in the 8000 PSI range.

Contact the manufacturer for proper weld repair.