This is a brand new aftermarket voltage regulator rectifier for the Kawasaki KX 250 and KX 450 motocross models of the 2013 generation. It is a direct replacement for the original unit: the body measures 75 mm long by 44 mm wide by 29 mm deep, the two mounting holes sit 61 mm apart centre to centre, and the single five-pin plug on a 160 mm lead matches the factory connector, so it is plug-and-play with no cutting, splicing or assembly needed.
RMSTATOR have specified an improved heat sink and increased charging capability over the original design, which matters on a competition four-stroke where the regulator sits in a hot, vibrating, dirt-blasted position and is expected to shed heat continuously. The opposite connector - the main harness side half of the plug - is supplied in the box, because on these machines it is very often found corroded or melted, and a marginal connection there is a frequent cause of a replacement unit failing in turn. Every regulator is tested before shipping.
Key Features
- Brand new aftermarket unit, not a rebuilt core
- Direct replacement for Kawasaki 21066-0721 and 21066-0742
- Improved heat sink and charging capability over the original design
- Matching main harness side connector supplied in the box
- Plug-and-play - one plug, five pins, five wires, 160 mm lead
- 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 |
RMS020-107257 |
| Width |
44 mm |
| Length |
75 mm |
| Height |
29 mm |
| Wire length |
160 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 |
2013-2016 |
| Kawasaki KX 450 |
2013-2015 |
OEM Part Number Cross Reference
Aftermarket replacement. OEM part numbers are listed for reference only.
| Part Number |
Manufacturer / Brand |
| 21066-0721 |
Kawasaki |
| 21066-0742 |
Kawasaki |
| RMS020-107257 |
RMSTATOR |
Frequently Asked Questions
Do I have to modify the bike to fit it?
No. It is a direct fit, plug-and-play replacement. The single five-pin plug, the 160 mm lead and the 61 mm mounting hole spacing all match the original Kawasaki unit, so no cutting, splicing or assembly is required.
What comes in the box?
The regulator rectifier and the opposite connector - the main harness side half of the plug. It is supplied because the harness connector on these models is frequently found corroded or heat-damaged, and reusing a damaged one will shorten the life of the new regulator.
How do I tell whether the old unit has failed?
Put a meter across the battery terminals with the engine running. A charging system in good order should read close to the regulated 14.5 V +/- 0.5 V shown in the specification table. A reading stuck at resting battery voltage means the unit has stopped charging; a reading above 15 V means it has stopped regulating and is overcharging the battery. Batteries that will not hold charge, blown bulbs and a browned connector all point the same way.
How does this differ from the later 2016 onwards unit?
This part covers the KX 250 from 2013 to 2016 and the KX 450 from 2013 to 2015, superseding Kawasaki 21066-0721 and 21066-0742. It is 29 mm deep with a 160 mm lead, so check the number on your original unit and the lead length before ordering.
Dispatched from the UK · 12-month warranty · Fitment support from our technical team
