prolly need a gearset if the internal motor is not messed up. those are not cheap. i'd say try the core with the gearset outta the HB. if it works fine, then go with it, now u have a spare core. heck go buy the plastic gear set from a HB and then u have 2 servos. most of the guys here who run the exotek R3 in 1/18 touring here use the HB over the MG, 1 because of cost (dont think any1 has killed a servo thats runnin the servo saver off ur vehicle) and b/c its a coarse (wood) thread unlike the mg which of course has that funky M2.3 thread or whateva. heck i live near maryland metrics (1 of the biggest if not biggest hardware warehouses in the country) and they didnt have a M2.3 to help me in stock. Alas i tapped it to M2.5. lotta grief to do that, never again, i was 1 of the 1st to deal with it at our track from them i steered (no pun) every1 else who needed 1 as those chassis became avail to go get the HB.

good luck

R