Sorry, I have looked on the forum for a thread, youtube, other sites, and other forums and I can't get a straight answer. What is the difference in a stock/ spec motor vs. a modified motor. Same brand, same turn, and same everything. Not race classes, but motors. For example a Hobbywing 540 can 10.5t stock spec motor and a Hobbywing 540 can 10.5t modified. Thanks in advance I've been looking for hours.

Assuming Roar rules, a spec motor has specific stator, winding & wire size, and rotor limitations. Modified has a different and far less restrictive rotor limit and not much else beyond the shared can size as far as I am aware.

Page 46 and 47 covers it I think, assuming no missing updates or something else I've overlooked: 2013 ROAR Rule Book

Thank you very much

Thought there was something I was forgetting. Added/clarified spec stator rule. Probably doesn't change much thou in regards to your question.

ROAR stator rule and announcement