We always broke our RM125's in with 3 heat cycles of 15 minutes each. First cycle start bike and ride around at various throttle openings up to 3/4 throttle with no constant throttle at any position for more than a few seconds, after 15 minutes let bike cool until rads/cylinder were cool to the touch. Cycle two same as cycle one but now with various throttle up to full throttle but still no constant throttle for more than a few seconds. Third cycle now that I think of it isn't really a cycle as we just ride it hard but stop after the final 15 minutes and let it cool down one more time.
Lots of different opinions on this but that is how we approached it, enjoy your new ride :ride: