How do I know if my MR-04 is Evo2?

The Evo2 board uses a revised front end design and the I.C.S. settings menu will show an RF Mode option with KOPROPO TLMY and Evo2 Mode as selectable values. Pre-Evo2 MR-04 boards do not have this RF Mode option. The Evo2 label is also printed on the chassis and the product box.

Why does RF Mode default to KOPROPO TLMY?

It's not clear. Some batches of Evo2 boards seem to ship this way regardless of what transmitter the buyer runs -- possibly a firmware default from a specific production run or retailer-side configuration. It's common enough that RF Mode is the first thing to verify on any Evo2 that's acting strange.

Will an MR-03 servo work in an MR-04?

No. The MR-03 servo (MZ408-2) and the MR-04 receiver/ESC unit are different parts that are not interchangeable. If you need to replace the servo or the receiver board on an MR-04, you need MR-04-specific parts -- specifically the MZ713 unit set for Evo2 boards.

Should I flip my MR-04 Evo2 king pins?

Probably not. Kyosho redesigned the MR-04 Evo2 front end to eliminate the sliding-knuckle friction issue that made the king pin flip necessary on the MR-03. If you're on an Evo2 and experiencing steering drift, king pin friction is unlikely to be the cause. Work the front suspension by hand and look for mechanical binding -- if it moves freely, move on to other causes.

Why won't trim hold my center on the Futaba 6PV?

Trim is a transmitter-side offset -- it shifts where your steering input starts, but it doesn't change where the servo thinks zero is. If the servo pot is worn, the servo's center reference is drifting, and trim can't catch it. If RF Mode is mismatched, the chassis may be interpreting your inputs slightly off-scale. Rule out both before assuming the pot is bad.

MR-04 Evo2 Steering Drift: Diagnose a Worn Servo Pot

This one comes up on the MR-04 side of the forum about as often as it does for the MR-03, but the diagnosis is different in one important way. The MR-04 Evo2 has an RF Mode setting that can produce steering symptoms indistinguishable from hardware failure — and it’s a software fix, not a parts order.

Start there before you touch anything mechanical.

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Running an MR-03? This diagnosis flow doesn’t apply to you — the MR-03 doesn’t have RF Mode. See the MR-03 steering drift article for that platform.

Step 1: Check RF Mode (Evo2 Boards Only)

The MR-04 Evo2 board has an RF Mode setting accessible via the I.C.S. cable. It controls which receiver protocol the chassis expects. The two modes most drivers encounter are Evo2 Mode (the correct setting for Futaba, KT-531P, and Sanwa) and KOPROPO TLMY (for Ko Propo EX-NEXT telemetry systems only).

The problem: a lot of Evo2 boards ship defaulting to KOPROPO TLMY. If you’re running a Futaba 6PV, the car will still bind, still drive, and nothing will look obviously broken — but the chassis is interpreting protocol signals under the wrong handshake. That can surface as steering that won’t hold center, subtle throttle feel differences, or drift that moves around session to session.

To check it, you need the Kyosho I.C.S. adapter. Connect the cable, open the Evo2 settings, find RF Mode, and confirm it’s set to Evo2 Mode. If it’s on KOPROPO TLMY, switch it, write the settings, power cycle, and re-pair.

The RF Mode article has the full walkthrough including a quick matrix of which transmitters use which mode. If you haven’t verified this setting yet, do it before anything else. It is a free fix if it’s the problem.

Step 2: Futaba 6PV Transmitter Reset

On the MR-03, this step covers the KT-531P reset flow. The MR-04 + Futaba 6PV combination is common enough to warrant its own procedure. Transmitter-side subtrim values and EPA settings can survive a normal trim reset and silently bias the steering — especially if the model file has accumulated cruft from previous configurations.

Work through this sequence:

Rebuild the model from scratch if you’re unsure whether the current model file is clean. It takes five minutes and removes any accumulated offsets.
Zero out trim and subtrim for the steering channel. Not just trim — subtrim specifically, which is the per-channel offset that survives power cycles.
Reset steering EPA to default (usually 100% both directions). A mismatched EPA can make the steering feel biased even when the servo is fine.
Check servo reverse. It sounds obvious, but accidentally reversed steering will produce a specific kind of wrong behavior: the car responds to inputs but drifts in the opposite direction from where you expect. Confirm the servo reverse flag for the steering channel is off.
Confirm failsafe position. On the 6PV, the failsafe should be set to neutral steering. If it’s set to any offset, the car will drift toward that position under any latency event.
Re-pair the transmitter and receiver after any settings change. On the Futaba side, re-binding after a model rebuild ensures the new neutral position is registered.

If the drift is gone after this, it was a radio problem. You did not need new parts.

Step 3: Front Suspension Check

The MR-04 Evo2 front end was redesigned specifically to address the sliding-knuckle friction issue that makes the king pin flip a routine fix on the MR-03. On an Evo2, king pin friction is low on the suspect list.

That said, it’s worth a quick check. Car off the ground, hold the chassis, and work the front suspension through its steering travel by hand. It should move freely and return to roughly center without mechanical bias. If you feel notchiness or it catches at any point, look for a bent steering rod or debris in the knuckle. A few minutes of visual inspection is faster than ordering parts you may not need.

If you’re on a pre-Evo2 MR-04 and experiencing this, the king pin flip article applies to your chassis. The Evo2 fix was specifically an engineering response to that issue.

Step 4: Battery Voltage

Same principle as on the MR-03: a servo that’s operating on low voltage can’t hold center reliably under steering load. Run the test on a known-good, fully charged pack and note whether the drift changes. If it does, voltage was the variable. Not glamorous, but worth eliminating.

Confirming the Pot Is the Problem

If steps 1 through 4 all come back clean, you are most likely dealing with a worn servo pot in the receiver/ESC unit.

The test: body off, car off. Rotate the steering horn through its full travel by hand. A healthy pot gives a clean, distinct center — you can feel it. A worn pot gives you an indistinct center, or the horn detents to a position that’s clearly off to one side.

Power the car on with the transmitter centered and no input applied. Listen. Buzzing, hunting, or repeated small corrections at rest mean the servo controller is getting inconsistent feedback from the pot and chasing a center it can’t find. That’s confirmation.

Fixing It

Important: MR-03 servo parts do not fit the MR-04. The MZ408-2 is an MR-03-specific part. If you search for “Mini-Z servo” and order the first result without checking the application, you will have the wrong part.

The correct replacement for the MR-04 Evo2 is the Kyosho RC Unit Set MZ713, which is the receiver/ESC assembly for the Evo2 board. It runs $60-80 depending on availability. This is the OEM path and it is stock-legal.

MR-04 specific parts can also be sourced direct from RCMart and KenOnHobby if Amazon availability is thin — these retailers carry Kyosho parts reliably and often have faster stock on current-production SKUs than the Amazon marketplace.

What This Is Not

A worn servo pot on the MR-04 is routine maintenance, not a platform problem. It accumulates wear proportional to steering travel logged — track-time cars need service sooner, shelf cars can go years on the original. The fact that the MR-04 Evo2 adds the RF Mode variable means you have one more thing to rule out before committing to parts, which is actually useful: it’s a free fix when it applies.

For broader MR-04 context, the MR-04 Platform Guide covers service intervals and what to check before each session. If you’re comparing the MR-03 and MR-04 platforms and trying to decide which one suits your situation, the MR-03 vs MR-04 buyer guide covers the practical differences.

Mini-Z Modder