Top end oilers are useful on modified high lift valvetrains. They supply supplemental oil to the critical high stress areas- rocker arms and cam lobes.
Aftermarket oilers are not needed on a stock machine. On a highly modified motor, they are a form of cheap insurance. Kind of like installing a high volume oil pump in your hot roded 350 small block.
They are very common on hot rodded GS1100/1150's. A quality unit properly installed will not give any problems.
Ride On, Ed.
2005 GSF1200SZ
1992 900SS
1983 GS750ED