Once had to do a helicoil on my old 250/8. Rolled it over to get a little clearance in the cyl in question. Pushed some cloth material in and after the thread cutting to accept the helicoil, I was able to pull out the material the cuttings with it. No problems installing the coil and ran ok thereafter.

Was precipitated by using antiseize and overtorqing, because the antiseize reduced torque requirement. Long ago and far away in the past...