This guide explains how to safely evaluate a used 72V ONYX RCR before buying.

It starts with fast visual checks anyone can do, then moves into deeper inspection of the battery, electronics, and drivetrain so you can avoid expensive surprises and unreliable builds.

If you verify only one thing, make it the battery.

Quick Overview

If you are short on time, confirm these first:

  • Seller provides proof of ownership
  • Battery health is verified with the BMS app
  • Bike was stored indoors during winter
  • No frame damage or sloppy wiring
  • Proper charger is included
  • Test ride in Sport mode is clean

If any of these fail, walk away.

Buy or Sell Safely

The ONYX AF Sales group is the safest marketplace for used bikes and a great place to verify sellers and pricing.

Used Buyer Caution

This post covers common scams, unsafe wiring jobs, and misleading listings from shops and private sellers.

Basic Bike Inspection

Inspect the bike in good lighting.

Look for:

  • Frame cracks, dents, bends, or crash damage
  • Rust in the battery compartment or around welds
  • Loose spokes or bent rims
  • Clean wiring (no electrical tape bundles)
  • No exposed copper or melted connectors

Have the seller ride the bike first:

  • Verify headlights, brake lights, and turn signals
  • Test regenerative braking
  • Listen for grinding or clicking noises

A clean bike is easy to spot. A problem bike is expensive to fix.

Odometer Check (MPH ↔ KM/H)

Sometimes mileage is reset.

To toggle units:

  1. Hold SET (bottom-left button) for 10 seconds
  2. Release
  3. Hold again for 10 seconds to switch back

Large changes in mileage are a red flag.

What to Ask the Seller

  • Two key fobs
  • Two wooden battery cover keys
  • Original charger (5A or 10A)
  • Proof of purchase (email or receipt)
  • BMS app password (if set)

Battery Health

Always confirm:

  • Battery was stored indoors during winter
  • No swelling or physical damage
  • Bluetooth connects successfully

ONYX 41Ah Battery

Healthy readings:

  • Cell delta between 0.005V - 0.080V
  • Stable voltage at rest
  • No sudden cutouts under load

Example BMS screen:

regular

ONYX 23Ah Battery

Not produced since Fall 2022.

Reality:

  • Best-case lifespan: ~2027
  • Poor storage shortens life quickly
  • More prone to voltage sag and early cutoffs

Test method:

  • Charge to ~72V
  • Full throttle in Sport mode
  • Watch for instant cutout or voltage collapse

Budget for replacement if it fails.

Charger

Verify:

  • Correct voltage for the 72V system
  • Fan operates normally
  • No error lights
  • Original connectors in good condition

Motor

Listen for:

  • Grinding
  • Clicking
  • Uneven whine

Inspect:

  • Phase wires near axle
  • Hall sensor cable
  • No heat damage or splices

Controller

Many used bikes have aftermarket controllers.

Confirm:

  • Amp limit matches the listing
  • Secure mounting
  • No burnt smell
  • Proper wire thickness

Suspension

  • Compress front and rear
  • No oil leaks
  • No clunking or sticking

Brakes

  • Pads not thin
  • Rotors not warped
  • Smooth braking with no noise

Electrical System

Red flags:

  • Twisted wiring
  • Electrical tape repairs
  • Random connectors
  • Exposed copper

Sloppy wiring often means internal problems too.

Throttle & Display

  • Smooth throttle response
  • No dead zones
  • Stable display brightness
  • No flickering

Tires

Stock sizes:

SizeNotes
2.75" × 17"Stock
3.00" × 17"Stock

Common brands:

  • Mitas
  • Michelin
  • Vuro

Wheels & Spokes

  • Spin wheels
  • No side wobble
  • Tight spokes

Aftermarket Parts

Acceptable only if:

  • Installed cleanly
  • Known brands
  • Seller explains purpose
  • Wiring remains tidy

Hub motor repairs deserve extra scrutiny.

Controller Tuning

Ask:

  • Stock or custom tune
  • Battery amps
  • Phase amps
  • Regen strength

Bad tuning can destroy batteries and motors.

Test Ride

Check:

  • Straight tracking
  • Smooth acceleration
  • No vibration
  • No hesitation

Top Speed & Torque

In Sport mode:

  • Strong pull
  • Stable power
  • No sudden dropouts

Ownership

Always require:

  • Bill of sale
  • Proof of ownership

Maintenance History

Ask about:

  • Battery charging habits
  • Winter storage
  • Tire replacements
  • Electrical repairs
  • Controller changes

If something feels off, it probably is. Another clean bike will always appear.