This is a quick reference article for anyone wanting to know how to replace gears on the 3001hv servos from BK.
Make sure you remove your servo horn. Pull apart servo by unscrewing the 4 LONG screws at the rear of the servo.
Take note of the gear positions or refer to the photos above for reference.
BE CAREFUL NOT TO MISPLACE THE TWO GEAR PINS: the long pin is for the two center gears and the short pin secures the cup gear on the left.
Pull off the old gears and be careful not to loose the gear pins. If you loose one you probably will have to buy a new servo.
Gear 3 has a D Notch and bearing on the servo body. Take note of the D notch position because you need to align Gear 3 to fit into the D notch while inserting the new gearset.
Make sure the small bearing for gear3 is positioned firmly in the servo body
Place the long pin through the two center gears. Do not put the pin in the cup servo (gear 2) yet.
While holding the center gears in your fingers, position gears 2 and 3 so that it resembles the assembly above. Remember that Gear 3 needs to be aligned with the D notch (otherwise you wont be able to push gear 3 all the way in). This is the tricky part - with the servo gears loosely positioned in one hand, fit them onto the top of the servo and ensure the center pin lines up with the center pin mounting point while ensuring that the main gear 3 is inserted into the dslot. Push down reasonably firm on the main gear to make sure it is properly home. Also make sure the bottom servo gear is meshing with the servo motor drive.
Be careful now! you can easily loose the cup gear so now is the time to Insert the small pin into the cup gear 2.
Put gear grease on the gears and re-assemble the casing. Check the servo function by reattaching the servo arm and spinning the servo arm gently. It should move without force.