RS550 GRS550VC 21V Motor – A quick fix for your cordless mini chainsaw
Did your motor give up in the middle of a project? Before you spend money on a brand-new tool, check if this RS550 GRS550VC motor can get you back up and running in under an hour. With 21V power and 28,000 RPM (no-load), it restores your mini chainsaw or portable electric saw to its original performance.
Note: Before purchasing, please carefully compare your original motor’s shaft diameter (3.2 mm), pinion dimensions, and mounting hole spacing (25 mm) with the specifications below. These measurements are critical to ensure compatibility with your specific tool model.
Why choose this model? (Key Advantages):
- 28,000 RPM (no-load) — Consistent speed that maintains cutting performance even when the wood offers resistance.
- 90W output at 21V — Delivers the same performance level as the original motors found in modern compact power tools.
- 1 Nm Torque — Provides sufficient power for repetitive cutting tasks without stalling or premature overheating.
- 14-tooth pinion, 8.2 mm diameter — Designed for a direct fit on most compatible mini chainsaw drive mechanisms, requiring no modifications.
- 3.2 mm shaft, 12 mm length — Standard dimensions for 20–21V cordless compact power tools.
- 25 mm mounting hole spacing — Ensures a secure fit into your existing tool housing without the need for additional drilling.
- Permanent magnet brushed DC construction — Proven technology that is easy to maintain and features widely available replacement parts.
Details and Performance
This motor utilizes permanent magnet brushed commutation, a classic architecture favoured in compact power tools for its immediate start-up response and predictable behaviour under load. At a 21V nominal voltage, it reaches 28,000 RPM (no-load) and maintains a stable 1 Nm torque during continuous cutting, preventing rapid thermal degradation. The 14-tooth pinion with an 8.2 mm diameter ensures precise power transmission to the chain or gear assembly, eliminating play and efficiency loss.
| Parameter | Value / Detail |
|---|---|
| Nominal Voltage | 21V DC |
| Max Speed (no-load) | 28,000 RPM |
| Output Power | 90W |
| Torque | 1 Nm |
| Motor Type | Permanent magnet DC, brushed |
| Motor Length | 75.1 mm |
| Motor Diameter | 37.2 mm |
| Shaft Length | 12 mm |
| Shaft Diameter | 3.2 mm |
| Pinion Diameter | 8.2 mm |
| Pinion Thickness | 6.8 mm |
| Mounting Hole Spacing | 25 mm |
| Pinion Tooth Count | 14 |
| Main Applications | Cordless mini chainsaws, portable electric chain saws, compact battery-powered cutting tools |
Package Contents
- 1x RS550 / GRS550VC 21V Electric Motor with 14-tooth pinion
Frequently Asked Questions
How do I know if this motor is compatible with my mini chainsaw?
Check three dimensions on your old motor: the shaft diameter (must be 3.2 mm), the distance between the mounting holes (25 mm), and the number of teeth on the pinion (14). If all three match, the motor will be a direct fit with no modifications required.
Can I power this motor with an 18V battery instead of 21V?
Yes, this permanent magnet DC motor will function at lower voltages. At 18V, you will achieve approximately 85–87% of the nominal speed—sufficient for light cutting, though you may notice a slight decrease in power compared to 21V operation.
How long does it take to replace the faulty motor?
With basic technical knowledge and a screwdriver, replacement typically takes between 20 and 40 minutes. Simply open the housing, disconnect the old motor from the two power wires, unscrew it from the mounting points, install the new motor, and reassemble. If you are not comfortable opening power tools, we recommend seeking professional service.
Does it work for other DIY projects besides chainsaws?
Yes. With 28,000 RPM and 90W, this motor is also used in miniature grinders, rapid-action drive mechanisms, or DIY prototypes that require a compact, high-speed DC motor. Its compact dimensions (75.1 mm length, 37.2 mm diameter) make it easy to integrate into custom projects.
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