Kyosho Mini-Z MR-03/MR-03EVO Delrin Servo Gears Upgrade

Kyosho Mini-Z MR-03EVO Today we are going to upgrade servo gears and tighten the servo saver. Why? Out of the box, there's quite a bit of slop with the steering rack. As a result, the car doesn't center 100% properly. In addition, there's slight gear binding toward the right steering end point, causing the servo motor to whine. I'm going to replace the servo gears with PN Racing Delrin Servo Gear Set (MR3093) which should be smoother and more precise. Because Mini-Z is tiny, the servo is integrated into the chassis. Accessing the servo mechanism means disassembling the whole car. There's some built-in slack with the stock gears. I'm actually surprised that MR-03 still manages to drive pretty straight. It's taken some time, but I'm now in position to remove the servo. Be careful with all the thin wires and solder joints. Here's a closer look at the stock servo. Fast forwarding the process of rebuilding the servo. All the gears look similar. The trick is knowing as a gear gets closer to the horn, which is slow and torquey, its teeth become larger and thicker to withstand the extra force. I'm using Kyosho metal servo fourth gear (MZW417) here. Turns out there's no need for the PN Racing Servo Gear Pin Set (MR3091). I can just reuse the stock pins. Putting the servo back together and testing for any gear binding. The delrin horn goes on next. Overall, the servo is straightforward to work on. It just takes a long time to get to it. This is also a good time to examine the servo saver mechanism. I want to tighten the spring to further reduce steering slop. Adding two 3.1x4x0.3 shims to preload the saver springs. Inspecting the servo carefully once again before putting it back into the chassis. Everything seems to be nice and smooth. I tried lithium grease and dry lube but I ended up removing them. The coreless servo motor feels pretty delicate. I'm not going to risk breaking solder joints by replacing the tiny pinion with the delrin version. With the metal fourth gear and delrin gears, plus adjustment to the servo saver, there is noticeably less play in the gear train. After getting the mainboard back into the chassis, it's important to test electronics again. Looks like the surgery was a success! Servo has become smoother and there's less slop. Music: "Straight", www.bensound.com