Toro Greensmaster Flex21 Resources

The Toro Greensmaster Flex21 walking greens mower is becoming a popular choice when lawncare enthusiasts decided to upgrade to a professional reel type mower to use on their home lawns. These are fantastic mowers that can provide an exceptional quality of cut and can last for a long time if properly maintained. There are pros and cons to this mower and equipped with the fundamentals of this mower, you can make the decision if this mower is right for your lawn.

Many enthusiasts purchase this mower due to the cost involved. These machines are often considerably cheaper than their Greensmaster 1000 and 1600 siblings. Prices of used greensmowers have seen a huge increase in the past few years due to their increased popularity and general awareness of how to obtain one. The purchase of a new greensmower is often not a possibility due to wife-leavingly high price tags of 10’s of thousands of dollars. This leaves the used market and the auction market. The quality of machines can be vastly different between these two. Typically, a used mower purchased from and dealer will be ready to go. Fresh grind on the reel and most mechanical issues sorted out. You will pay a premium for these mowers. The auction scene can be cheaper, but the mower will come AS-IS and may or may not need extensive repairs or maintenance. It is always advised to check out any equipment prior to entering a bid. My Flex 21 came from an auction and outside of a backlap and oil change it was good to go.


The Flex Series greens mowers are generally cheaper, but awareness of the limitations of these mowers must be known. The reason for the cheaper price is often due to the height of cut (HOC). The earlier Flex21 units had a maximum HOC of around ½ inch (12.7mm). This HOC limitation can be remedied by adding a High HOC kit. This will increase your maximum HOC to around 1 inch (25.4mm) but is also limits your minimum HOC to around ½ inch (12.7mm). Many units also come equipped with a groomer. The groomer is a great tool to help with many quality of cut issues, but come with the limitation of not being able to utilize the high HOC kit. If the limitation of the HOC is not an issue then you can save some money by going with the Flex Series.

Why It's Awesome

The greatest advantage of the Flex 21 is the lack of needing to grease. The Greensmaster 1000 and 1600 series mowers require periodic greasing. The only time you would have to grease a Flex 21 is if the mower is equipped with a groomer. That add-on requires re-greasing for proper maintenance. The only required maintenance for the Flex 21 is your typical fluid and filter changes and recommended intervals.

The second advantage of the Flex 21 is the “floating” cutting head. This functions in a similar manner to the cutting heads of a triplex. The reel is separate from the traction unit and attaches to mount points that pivot to allow for a floating action over the lawn. This feature allows the mower to contour to uneven surfaces and undulations of the mowing surface. Ultimately resulting for the potential of a greater quality of cut.

Scheduled Maintenance

The remainder of the maintenance for a Flex 21 is like your typical maintenance. Here is a brief overview of maintenance schedules for the Flex 21.

  • Oil Changes- Check the oil level after every 5 hours of operation. The initial oil change is after 20 hours with subsequent changes every 50 hours of operation.
  • Air Cleaner- Clean the foam pre-cleaner after 25 Hours and replace the paper filter every 100 hours of operation.
  • Fuel Filter- Clean initially after 20 hours and then every 50 hours of operation.
  • Spark Plug- Check the condition of the spark plug every 100 hours and replace if necessary.
  • Gearbox- Replace the transmission fluid after the first 50 hours of operation and every 2 years thereafter.

There are also four belts that will need to be replaced on the Flex 21. Two of the belts are on the Traction unit that control the rear drum. (P/N: 99-2023) and the other two belts (P/N:99-2022), one on the cutting unit and the other on the gear box control the reel. All of the belts are toothed belts and have a fairly long-life span.

The recommended oil varies based on operating conditions. This chart outlines the recommended oil viscosities based on the conditions the mower will operate in. The oil capacity of Kawasaki FE120 is 20 ounces (.6 liters)

Oil Type Based on Operating Temps

 The gearbox on the Flex 21 requires a Dexron III Automatic Transmission Fluid or equivalent and has a capacity of 2.9 quarts ( 2.78 liters).

The spark plug recommended is a NGK BPR 5ES or equivalent. The plug gap should be set with a feeler gauge to a gap of .028 to .032 inches ( .7 to .8mm).

You Will Probably Break Some Parts

One thing that must be realized is that these mowers are not new. Yes, they are robust and designed to be used daily for several hours at a time, but they do age. The most common part I have seen fail are the cables that control the traction unit, reel engagement, and parking brake. The ends of the cables are adjustable to make up for extra slack as the cables stretch over time. The adjustment is simple, but the metal used deteriorates over time and becomes brittle and will break if too much stress is place on it. Ask me how I know that!! The most common one to break will be the reel engagement cable. Here are the part numbers for when you break yours.

  • Cable-Clutch Traction: 105-5328
  • Cable-Clutch Reel: 99-3765
  • Cable-Brake: 99-6214

Reel Replacement

Making the switch to a professional greensmower from a standard reel mower like a McLane or TruCut is a monumental leap. I hope this helps on your journey in the lawn and the joy that is reel mowing. Please be sure to leave a comment with any questions.

4 Responses

  1. Reel Low Dad,
    I am on the hunt for the service manual for a 4202-270002077 cutting unit….you wouldn’t happen to have a link or a copy of this cutting unit model service manual, would you? My traction unit is a 4022-270001963. Any help in the right direction is greatly appreciated.
    Thanks for the youtube content as well, we enjoy it!

    1. I do not have a copy of that pa1rticular unit’s manual. I would check out, I am pretty sure they have one there.

  2. I have a toro flex 21 and have a high of cut kit that I need to install do you have any experience with this or have you seen a guide on how to install?

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