Why remove them....why not make use of them to mount your engine.It's better than drilling the frame.
The idea was to make up a bracket so that the bracket bolts to 2 drink bottle studs then the engine bolts to the bracket...2 studs and an aluminium bracket means any stress is distributed over a much wider area.I tried that. It worked ok, but not the greatest. It is just a tiny screw.I had to use extra long studs for the rear mount, because of the thickness of my frame. I don't think I used strong enough studs. The rear mount bolts sheared. . After that it ripped the water bottle screw and threads right out the frame. The motor almost fell off the bike completely.