€1,079.00
Available, delivery time: 1-2 weeks
Product "Kawasaki Ninja 400 Racing Alternator Kit 2018+"
Kawasaki Ninja 400 Racing Alternator Kit 2018+ – without comfort relay is the version of the BDK Racing alternator kit for the KAWASAKI Ninja 250 / 300 / 400 (2018–2026): lightweight rotor for reduced gyroscopic forces on the crankshaft and faster downshifting, without comfort relay (electrical consumers are disconnected) – for the racetrack and racing conversions.
Fits KAWASAKI Ninja 250 / 300 / 400 2018–2026.
Each unit includes rotor, stator with mounting plate and regulator, all connectors pre-fitted.
(RG-KAW-NIN400-18+ .2, BDK Racing Lima)
Please select your preferred variant and the matching accessories for installation and successful operation!
This is a complete, ready-to-fit kit consisting of the rotor, the alternator coil including the corresponding mounting plate, and the alternator regulator. The kit is supplied pre-assembled with all necessary connectors.
In short: The significantly lighter rotor, with a smaller radius, results in substantially reduced gyroscopic forces on the crankshaft. The effect is immense:
- Easier direction changes, especially in chicanes
- Significantly faster matching of engine speed when downshifting under braking, resulting in:
- Faster downshifting
- Less instability, a more stable rear end
- More time and comfort when turning in
- Later braking
- Improved throttle response, faster acceleration
The typical power gain is approximately 3 hp, although this varies from engine to engine.
This kit uses a rotor with a diameter of 80 mm and a weight of only 294g.
This not only reduces the effective weight of the crankshaft, since the new rotor is 75% lighter than the original rotor (1,210g), but above all reduces gyroscopic forces thanks to the significantly smaller radius of 80mm instead of 120mm. A practical example to illustrate the effect: at 14,000 rpm, a standard rotor reaches a rotational speed of 320 km/h due to its larger radius, whereas the kit rotor reaches only 209 km/h.
The main performance benefits stem from the fact that a lighter rotor with a significantly smaller radius is much easier to accelerate and decelerate.
Most racing alternators also use a smaller rotor, but compared to ours, usually with significantly fewer windings in the coil, resulting in uneven and relatively low output. In addition, the original regulator is often retained, which is not designed for the excess power generated at the required revs and can only convert this into damaging heat.
Our alternator kits also use a small rotor, but we use a particularly efficient and fine wire for our windings. This allows us to deliver strong, consistent power from lower revs onwards (approx. 4,000 rpm).
Another clever feature lies in the switching system of our special alternator regulator. Once the desired voltage is reached, no further electricity is generated at the crankshaft. This results in a significantly cooler and more durable regulator. For this reason, you should never use our alternator kits with the original regulator.
Particularly in view of the specific requirements regarding the necessary capacity reserves in conjunction with a racing alternator, we recommend using a LiFePO4 supply battery with a minimum of 7.5 Ah, preferably 10 Ah.
We advise against using a lithium polymer battery in combination with a racing alternator.
To remove the original flywheel, you will need a puller.
Pullers and LiFePO4 batteries are available here in the shop.
Important installation notice
for racing alternator kits from BDK Race Engineering
A BDK racing alternator kit replaces your motorcycle's rotor, stator and regulator/rectifier with a significantly lighter unit designed for racing use. This provides a noticeable reduction in rotating mass – but requires careful installation and involves changed operating behaviour. To ensure your kit works reliably from the outset, here is an overview of the most important points.
Who should carry out the installation?
Installation should be carried out by an experienced mechanic – someone who is confident working on the engine and the vehicle's electrical system. Specifically, this includes:
- Removal of the alternator cover, flywheel/rotor, starter clutch and stator, including securing the Woodruff key (rotor key)
- Removal and refitting of the ignition pulse sensor (pickup), maintaining the original installation position
- Working with thread locker and specified torque values according to the manufacturer's instructions
- Cleaning sealing surfaces, correctly fitting new gaskets and locating dowels, and sealing the cable grommet
- Professional crimping of the spade connectors and fitting of the connector housing
- Connection and fusing of the regulator/rectifier in the vehicle electrical system, plus measurements with a multimeter in AC and DC
What matters during installation
- Thread locker is mandatory: All screws must be fitted with thread locker and tightened to the specified torque. Failures have already occurred due to missing thread locker – this is the most common avoidable mistake.
- Only use the supplied regulator: The standard regulator must never be used with a racing alternator. The regulator body must have a permanently clean earth connection.
- Regulator mounting: on a flat metal surface exposed to airflow, away from exhaust heat. One mounting point bolted, the second secured with a cable tie.
- Pay attention to cable management: Route the stator and pickup wires and secure them with the original clamps as done from the factory – free of chafing, with sufficient movement clearance, and not pinched. A chafed cable causes a short to earth.
- Connectors: Every spade connector must click audibly into place. The order of the three stator wires is not important – a secure fit is what counts.
- Fusing and switched positive: An intact fuse (30 or 35 A depending on kit) must be fitted in the positive line. The signal wire must be connected to a switched 12V positive supply so that no standing current flows when parked.
- Follow the original installation instructions: Sequence, torque values, gasket part numbers and cable lengths are model-specific and are detailed in the enclosed BDK instructions.
What changes during operation
A racing alternator deliberately delivers less charging output than the standard system. Depending on the kit, it only starts charging from around 3,000 to 5,000 rpm; prolonged running at lower engine speeds will discharge the battery. This results in three fixed rules:
- Always start with a fully charged battery, using at least a 7.8 Ah LiFePO4 battery, ideally 10.4 Ah.
- After each session, remove the fuse at the regulator, disconnect the 12V supply, or use a battery disconnect switch – otherwise deep discharge may occur.
- Never start or run the bike with the battery disconnected or the regulator unplugged. This will damage the alternator.
The green LED on the regulator indicates that charging is taking place – a useful quick check before and after each session.
Diagnostics
The installer should be able to independently check with a multimeter: the fuse and switched positive supply, continuity between the stator pins (present between each other, none to earth), the AC voltage between the stator pins at a constant engine speed, and the charging voltage at the battery. This allows almost all faults to be narrowed down within a few minutes – often to something minor such as a blown fuse or a connector that hasn't clicked into place. The specific target values can be found in the troubleshooting section of the enclosed instructions.
If you're unsure
That's not a problem – in this case, please have the installation carried out by a specialist workshop or an experienced racing mechanic. If you have any technical questions about your kit, we'll be happy to help; just get in touch with us.
Please note: This is racing equipment intended exclusively for competition and track use and is not approved for use on public roads. In its development, performance takes priority over durability; as is common for racing parts, the manufacturer provides no warranty or liability for these parts, in particular not for consequential damage. Your statutory rights against us as the seller remain unaffected. The original installation instructions from BDK Race Engineering supplied with the product are authoritative for installation.
Compatibility
| Brand | Model | Years |
|---|---|---|
| Kawasaki | KAWASAKI Ninja 250 / 300 / 400 | 2018-2026 |
Installation Intro
Preview of the installation manual: introduction, safety rules and scope of delivery.

Manufacturer: B.D.K. Race Engineering, Norwich (UK) Fitting Instructions
BDK Race Generator Kit
These instructions take you step by step through removal, fitting, electrical connection, commissioning and testing of the kit. With the Ninja 400 kit the original generator cover is retained: the racing stator is mounted on a mounting plate, the pick-up gets spacers, the BDK rotor is bolted to the original starter clutch, and the stator lead is cut to length and fitted with crimp pins. They supplement BDK's short English fitting instructions with test values, a sign-off checklist and practical experience. Please read in full before you start.
- Fit all screws with thread-locking compound and tighten to the specified torque. Failures have occurred without thread-lock – this is the most common avoidable mistake.
- Rotor bolt ≈ 34 Nm (BDK: 25 ft·lb) with thread-locking compound; tighten the six M6 × 12 to the starter clutch only afterwards (centring).
- Use only the supplied racing regulator/rectifier. The original regulator destroys the race generator. The regulator housing must be properly earthed.
- Blue sense wire to switched positive 12V supply (ignition live). Permanent live drains the battery when parked, missing live prevents charging.
- Pick-up with 10 mm spacers (M6 × 20) and wires routed as from the factory with the original clamp – nothing pinched. And: never run the engine with the battery disconnected or the regulator unplugged.
Contents
1Before you begin – requirements & safety
A BDK race generator kit replaces the rotor (flywheel), stator (coil) and regulator/rectifier with a significantly lighter unit designed for race use. The lightweight rotor saves a large part of the rotating mass of the original generator – you feel it when tipping into corners, when downshifting and in throttle response. The price: the system demands a careful installation and changed operating behaviour (Section 9).
What you should be confident doing
- Removing the fairing, generator cover and flywheel with a puller – without force and without damaging gasket faces; separating the flywheel and starter clutch
- Removing and refitting the ignition pick-up with spacers
- Working with thread-locking compound and a torque wrench in the 5–35 Nm range
- Clean the sealing faces properly, fit the new paper gasket and locating dowels correctly
- Vehicle wiring: identify the switched positive, tap it cleanly and insulate it; fit crimp pins properly and populate the connector block
- Measuring with the multimeter in AC, DC and Ω (continuity)
If you are unsure about any point
Have the installation carried out by a specialist workshop or an experienced race mechanic. A mistake here can cost the rotor, stator, regulator or, in the worst case, the engine. If you have technical questions about the kit, we are happy to help before installation – contact details are on the last page.
These instructions are deliberately detailed. Experienced mechanics can skim the basics; the points in bold and the test values apply to everyone.
- Let the engine cool down completely. Support the motorcycle securely (rear paddock stand, front stand if necessary), ignition off, remove the key.
- Disconnect the battery first – always undo the negative terminal first and connect it last when reconnecting. With lithium batteries, never lay tools across both terminals.
- The generator cover is oil-wetted. Drain the engine oil before opening (Step 1) – this way only residual oil runs out when the cover is removed, the gasket faces stay dry and the bearing area stays clean. Have a drain pan, rags and gloves ready; remove any oil on tyres or brakes immediately.
- The rotor is a permanent magnet: swarf, screws and metal debris are attracted to it. Before fitting, dab the magnet side thoroughly with adhesive tape and check it.
- Use thread-locking compound, silicone remover and sealant only in ventilated rooms; observe the safety data sheets.
2Check kit contents & ordered option
Check the contents completely before you strip the motorcycle. If anything is missing or a part is damaged, do not start the installation – contact us.
| Item | Qty | |
|---|---|---|
| Racing stator windings assembly (stator) with cable sheath | 1 | |
| Rotor assembly (lightweight rotor, bolted to the original starter clutch) | 1 | |
| Mounting plate for stator windings assembly | 1 | |
| Spacers 10 mm for the ignition pick-up | 2 | |
| Racing regulator/rectifier with connection leads, green LED, fuse holder (35 A) and adjustment screw | 1 | |
| Screws M6 × 12, button head (rotor → starter clutch) | 6 | |
| Screws M5 × 30, button head (stator assembly → mounting plate) | 6 | |
| Screws M6 × 10, low head (mounting plate → cover) | 3 | |
| Screws M6 × 20, button head (pick-up with spacers) | 2 | |
| 3-pin connector block with pins | 1 | |
| Thread-locking compound, small bottle | 1 | |
| Original fitting instructions from BDK Race Engineering (“Kawasaki NINJA 400 Race Generator Fitting Info”, English) | 1 |
Your ordered option (please tick)
| Comfort Relay | yes – nothing needs to be disconnected after use no – battery or regulator is disconnected after use |
| Connection | Ring terminals directly to the battery (there is no OEM-connector conversion for Kawasaki) |
New cover gasket (genuine Kawasaki part), silicone sealant for the grommet, silicone remover, flywheel puller to suit the model (available in the shop), engine oil with sealing washer for the drain plug, and the recommended LiFePO4 battery (min. 7.8 Ah, better 10.4 Ah). A battery isolator switch makes sense if you have not ordered a Comfort Relay (Section 9).
- The original cover is retained; the stator goes onto the BDK mounting plate, the pick-up is refitted with 10 mm spacers and M6 × 20.
- The BDK rotor is bolted to the original starter clutch with six M6 × 12 – rotor bolt ≈ 34 Nm first, then the starter clutch bolts.
- The original grommet and approx. 40 mm of original wire are retained; the new stator lead is cut to length, sheathed and fitted into the connector block with crimp pins. According to BDK, bolt the regulator to metal through both holes.
The complete installation manual (10 pages) is included in print with every kit.












