AS 531 4T MK B Professional 53 cm Kawasaki Mower

The AS 531 4T MK B is a fully equipped 53 cm professional mower built for contractors who need dependable collection, clean handling and strong safety features across mixed sites. It runs the Kawasaki FJ180V KAI engine, giving steady power in damp grass and daily stop-start conditions while keeping fuel use predictable over long shifts.

This version includes the complete AS safety package, with an automatic parking brake and limited-slip differential for confident control on banks and uneven ground. The blade clutch, V-handlebar and 75-litre collection bag make it a practical choice for grounds teams, estates and commercial landscapers who want a mower that can deal with real-world conditions without slowing the job down.

What the AS 531 4T MK B Is Built For

The AS 531 4T MK B is designed for contractors and grounds teams who need a mower that delivers a clean, collected finish while staying safe and predictable on uneven or sloped terrain. It has the same core strength and cut quality as the standard MK version, but the MK B adds the full AS safety system, making it the preferred choice for commercial teams working across multiple sites each day.

This model suits the type of work where you’re constantly shifting between tight areas, paths, soft ground and banks. The Kawasaki engine keeps a consistent blade speed even when the grass thickens, and the deck maintains strong airflow to keep the 75-litre bag filling cleanly. For contractors with varied jobs and different operators, the MK B’s control layout and safety behaviour take a lot of the risk out of the day-to-day work.

Who This Model Suits

• Commercial landscapers needing a reliable 53 cm collector as their main mower.
• Grounds teams for schools, estates, campuses and parks.
• Contractors working around the public where safety features matter.
• Operators moving across uneven or damp slopes where traction is key.

Why It Works Well on Real Jobs

The automatic parking brake is a genuine advantage on slopes. The moment the blade clutch lever is released, the mower stops and holds itself, which gives you far more control when repositioning on banks or working in awkward spaces. The limited-slip differential allows both wheels to pull together, reducing wheelspin on damp or uneven surfaces. Combined, these features make the MK B feel steady and predictable in areas where most professional mowers get nervous.

The V-handlebar keeps everything easy to reach. The right hand manages the drive, brake and blade clutch, while the left hand fine-tunes your forward speed. The vibration damping makes long shifts easier on the arms, and the mono-bar design means emptying the bag is quick and doesn’t require wrestling with the handlebar frame. When you’re clearing dozens of bags in a day, these small details add up fast.

Where It Sits in the AS Range

The MK B is the “full-spec” professional collector in the 53 cm petrol range. It shares the same deck, engine choice and 3-in-1 cutting ability as the standard MK, but the full safety package is what lifts it above the base model. It sits below the 2-stroke versions in slope capability and below the 4WD RB in extreme conditions, but for a general-purpose contractor mower, this is the model that covers the most situations without compromise.

Optional Extras and Practical Add-Ons

• Tilt Meter: Useful when working on banks to keep work within safe angles.
• Hour Meter: Helps with maintenance intervals and contract reporting.

Operational Realities Worth Knowing

The MK B is at its best when used at sensible ground speeds, especially in damp grass. The 4-stroke engine copes well with daily commercial workloads, but it’s not designed for constant steep banking—contractors doing this will still benefit more from the 2-stroke or 4WD models. The mower’s 61 kg weight gives stability on slopes, but be aware that moving it without drive engaged takes more effort than lighter domestic machines.

Blade sharpness and deck condition have a big effect on collection performance. When maintained properly, the MK B gives strong bag fill and reliable cut quality throughout the season. Fuel use is predictable, and the 3-litre tank provides a workable runtime for shift cycles, with most contractors refuelling between sites rather than during a job.

How Suffolk Mowers Supports Your AS 531 4T MK B

Buying the AS 531 4T MK B from Suffolk Mowers gives you access to a dealer that understands the AS range and works with these machines every week. Before it leaves our workshop, we set it up properly, confirm blade alignment, check the control system and ensure the safety brake and differential lock engage exactly as they should. If you’re comparing it with the standard MK, the 2-stroke models or the 4WD RB, we can walk you through the differences and match the mower to the type of work you’re doing.

Our workshop handles all ongoing servicing, blade sharpening, belt replacements and general repairs. The Kawasaki FJ180V KAI engine is well supported in the UK, and we keep filters, blades, belts and common wear parts in stock. If you’re running a team, we can help you set up a maintenance schedule and show operators the simple daily checks that keep the machine performing at its best.

We also supply accessories such as tilt meters, hour meters and replacement bags, and we source additional AS parts quickly when needed. For contractors who rely on this mower every day, we can help you hold the right spares in your van to reduce downtime during busy periods.

AS-Motor offers up to a 2-year professional warranty when serviced through an authorised dealer. Suffolk Mowers handles all warranty inspections and claims directly, so if anything develops, you can bring the machine to us and we’ll manage the process while keeping you working.

Technical Specifications

Frequently Asked Questions About AS 531 4T MK B

The MK B includes the full AS safety package: automatic parking brake, automatic limited-slip differential and enhanced control layout. It offers better stability and safer handling on slopes and uneven ground.

Yes. The automatic parking brake and limited-slip differential make it far safer and more predictable on banks than most 4-stroke mowers. For very steep or consistently wet banking, a 2-stroke model is still the better choice.

Yes. The mulch kit is included and fits without tools. You can switch between mulching, collecting and rear discharge depending on ground conditions.

Definitely. It allows you to stop the blade without stopping the engine. This saves time when emptying the bag, crossing paths or moving between areas with obstacles.

Yes. It’s widely used in contractor machines because it handles stop-start work well, produces good torque in thicker grass and is straightforward to service.

AS-Motor offers up to a 2-year professional warranty when serviced through an authorised dealer. Suffolk Mowers manages the claim process directly.