Quick Answer
The Stihl RB 400 DIRT BOSS® is a gas-powered pressure washer with a 196 cc engine (6.5 hp) delivering 2,700 psi at 2.7 gallons per minute. It is designed for cleaning equipment and residential driveways, but forum reports indicate the unloader valve may clog under certain conditions, shutting down the machine. This article explains the key specs, real-world tradeoffs, and actionable steps to use the RB 400 effectively.
Main Explanation
Key Specifications
- Engine: 196 cc (6.5 hp) - Pressure: 2,700 psi - Flow: 2.7 gallons per minute - Hose: 25-foot no-kink flex hose ### Real-World Use Case (According to Forum Reports)
Based on a discussion on LawnSite, an owner plans to use the RB 400 mainly for cleaning equipment and washing a few residential driveways. The same thread notes that the machine will eventually clog and shut down. This suggests that while the unit provides adequate power for routine cleaning, regular maintenance of the unloader valve and inlet filter is critical to avoid shutdowns.
Performance Tradeoffs
- Strengths: High pressure and flow suitable for stubborn dirt on mowers, tractors, and concrete. The 6.5 hp engine provides enough power for continuous use on medium-duty residential tasks.
- Weaknesses: Potential for clogging (unloader valve) based on a single owner's experience. The clogging claim is from a forum post and should be treated as user-reported, not lab-verified.
Comparison to Similar Models
The RB 400 sits between lighter residential units (e.g., RB 200) and heavier commercial models. It lacks the higher flow rates (e.g., 3.5+ GPM) of professional washers but offers a balance for homeowner-heavy use. The closest alternatives in Stihl's lineup include the RB 600, which has a larger engine and higher output, but the RB 400 represents a sweet spot for price and performance in the $579.99 range (as of a 2017 forum mention).
Practical Takeaways
Steps to Use the Stihl RB 400 for Equipment Cleaning
- Prep the machine: Check oil level (engine lubricant), fuel level (unleaded gasoline), and water supply connection. Ensure the inlet filter is clean to prevent debris from entering the pump.
- Start the engine: Follow standard small engine startup, prime, choke, and pull start. Allow the engine to warm up for 30 seconds before engaging the spray.
- Select nozzle: Use a 40° nozzle for detergent application or general rinsing, and a 25° nozzle for removing dirt from equipment (e.g., mower decks). Avoid 0° turbo nozzles on painted surfaces to prevent damage.
- Clean equipment: Hold the nozzle 12–18 inches from the surface. For thick mud or grease, pre-treat with a degreaser and let it sit for 2–3 minutes.
- Prevent clogging: After each use, flush the system with clean water (with the engine running and spray trigger open) for 30 seconds. If the machine shuts down unexpectedly, inspect the unloader valve and inlet screen for obstructions.
- After every 50 hours of use, replace the spark plug and air filter.
- Use pump saver/antifreeze during storage if temperatures drop below freezing.
- Only use non-ethanol fuel to reduce gum formation in the carburetor.
Maintenance Tips
Bottom Line
The RB 400 is a capable gas pressure washer for homeowners who need to clean equipment and driveways regularly. Its 2,700 psi and 2.7 GPM provide enough power for most residential chores. However, be aware of potential clogging issues (based on forum reports) and practice regular maintenance to avoid downtime.
