I haven’t had to service my starter (yet), but I understand the starter is the same as that for the Leopard engine, even if it’s mounted a bit differently. The Leopard manual has a procedure, including helpful hints on retaining the brushes during rotor replacement and securing the brush wires with silicone:
http://www.artkart.lt/championkart/manual.pdf page 35
On my starter, which AFAIK is still functional, I get 0.5 Ohms between the power plug and a randomly-chosen bolt head on the engine (hey, I’m a Mechanical Engineer, not Electrical, OK?). Dunno if that’s a significant difference, considering how beat-up my multimeter is. Is there any sign the starter is even trying to turn? Is the reducing gear seized up with gunk? The one time my starter wouldn’t crank, the fix was a new battery and dielectric grease on the terminals. I know you say your battery is new, but stranger things have happened… Consider getting a spare battery (you should have one anyway) and try it or someone else’s “known good” battery before doing any serious teardown.