This is a brand new aftermarket voltage regulator rectifier for the Kawasaki KX 250 and KX 450 motocross models built between 2016 and 2024. It is a direct replacement for the original unit: the body measures 76 mm long by 44 mm wide by 22 mm deep, the two mounting holes sit 61 mm apart centre to centre, and the single five-pin plug on a 270 mm lead matches the factory connector. Fitting is plug-and-play, with no assembly, no cutting and no adapters required.
RMSTATOR also supply the opposite connector - the main harness side half of the plug - in the box. On these machines the harness-side connector is very often melted, corroded or otherwise damaged by the time the regulator itself gives up, and a marginal connection there is a common cause of repeat charging faults. Replacing both halves at the same time removes the resistance and the heat that killed the original. The regulator is built from a higher grade of electrical components than the original equipment, and every unit is tested before it is shipped.
Key Features
- Brand new aftermarket unit, not a rebuilt core
- Direct replacement for Kawasaki OEM part 21066-0743
- Matching main harness side connector supplied in the box
- Plug-and-play - one plug, five pins, five wires, 270 mm lead
- Higher grade electrical components than the original equipment
- Regulated output of 14.5 V +/- 0.5 V
- Rated to 50 A / 500 W maximum charging current
- Every unit individually tested before dispatch
Technical Specs
| Specification |
Detail |
| Part number |
RMS020-107251 |
| Width |
44 mm |
| Length |
76 mm |
| Height |
22 mm |
| Wire length |
270 mm |
| Fixation hole spacing (centre to centre) |
61 mm |
| Number of plugs |
1 |
| Number of pins |
5 |
| Number of wires |
5 |
| Minimum charging voltage |
14.5 V +/- 0.5 V |
| Maximum charging current |
50 A / 500 W |
| Open circuit voltage |
Less than 15 V |
| Operating temperature |
-20°C to 85°C |
Vehicle Fitment Guide
| Make & Model |
Years |
| Kawasaki KX 250 |
2016-2024 |
| Kawasaki KX 450 |
2016-2024 |
OEM Part Number Cross Reference
Aftermarket replacement. OEM part numbers are listed for reference only.
| Part Number |
Manufacturer / Brand |
| 21066-0743 |
Kawasaki |
| RMS020-107251 |
RMSTATOR |
Frequently Asked Questions
Does anything need modifying to fit it?
No. This is a direct fit, plug-and-play replacement for the original Kawasaki unit. The single five-pin plug, the 270 mm lead and the 61 mm mounting hole spacing all match the factory part, so no cutting, splicing or assembly is needed.
What is included in the box?
The regulator rectifier itself, plus the opposite connector - the main harness side half of the plug. RMSTATOR include it because these connectors are frequently found melted, corroded or defective, and fitting a new regulator into a damaged connector simply repeats the fault.
How do I know the old regulator has failed?
Check the voltage across the battery terminals with the engine running and compare it with the regulated 14.5 V +/- 0.5 V listed above. A reading that stays at resting battery voltage means the unit is not charging; a reading well above 15 V means it is no longer regulating and will cook the battery. Repeatedly flat or swollen batteries, blown bulbs and a scorched or discoloured connector are all symptoms of the same problem.
Is the same unit used across the whole 2016-2024 range?
Yes. RMSTATOR list this part for both the KX 250 and the KX 450 across 2016 to 2024, superseding Kawasaki part number 21066-0743. Confirm the number stamped on your original unit before ordering.
Dispatched from the UK · 12-month warranty · Fitment support from our technical team
