The 652cc V series engine had a few changes from the M series engine it was based on. One of these was stud mounts for the fuel pump and the engine breather/ oil filler rather than the bolts used on the M series.
As the stud mounts make it easier to fit the relevant accessories the SPOG produce stud conversions for the M series engines that replicate those found on the V series – as shown below from the Haynes Manual for the Visa.
