Mower deck maintenance – Toro MX 4250

The deck is a fabricated deck on a Toro MX 4250 residential zero turn mower, it has 200h of service over 8 years… which is not very much.

The deck has the recycler option installed.

Deck service included:

  1. Fit new bearings to spindles;
  2. Replace both idler wheels (components are not serviceable);
  3. Clean and apply corrosion protection under deck;
  4. Procure, fit and balance new blades; and
  5. Procure spare drive and deck belts for spares.

Spindle bearings

Jiggling the blade tips showed 2-3mm vertical play in both spindles. New bearings have much less play, undetectable without instruments.

The spindles are easily serviced.

The lower bearing is one spindle had a rusted retainer / separator and collapsed when driving it from the housing. The other lower bearing was rough, but did not collapse. The top bearings were in good condition.

A set of four NSK 6203-2RS bearings was purchased ($35) to replace all the bearings.

Idler pulleys

Both idler pulleys were dry of grease. It was possible to pop the rubber seal and pack a little more grease pending arrival of replacement parts.

Replacement parts were purchased for $60 (inc shipping) and fitted.

The message is that water sprayed over the top of the deck assembly is retained in a shallow cup on the sealed bearings and some will wind up inside the bearings… don't wash the top of the deck.

Deck clean, descale and corrosion protection

Above, the underside of the deck after washing, de-scaling with a pneumatic needle scaler, power brushing with a cup brush, and another high pressure wash ready for application of corrosion protection.

There are other options for rust removal, but in this instance the many advantages of a pneumatic needle scaler prevailed. The technique could not reach the interior of the recycler deflectors, so on the next maintenance, they will be removed and the interior flame de-scaled.

Above, a pack of Lanotec Steel-seal was purchased. It turned out to be way to thick for the pump spray pack shown and was brushed on. The incompatibility of the Steel-seal and supplied pump pack hints some quality control issues.

I have no idea of the shelf life of this stuff, there is no expiry date on the container, no reference in the datasheet.

It may be possible to dilute the Steel-seal for spraying, but there is no mention of a compatible solvent or directions on the pack or in their datasheet.

Above, the deck after brush application of Steel-seal.

Though a proprietary product is recommended for cleanup, I used ULP and it worked just fine (though it dissolved the printing on the pump spray bottle).

Time will tell how good a coating this is, whether it makes washing wet compacted grass out and the extent to which it protects against rusting.


I asked Lanotec about some of the issues raised here. They say

With respect to your experience with the sprayer, depending on the ambient temperature, in cooler conditions, due to the viscosity of the product it will thicken, as you would expect, potentially creating the issue you have experienced. If the product has not been shaken well you will find the evaporative carrier has not effectively blended with the core product significantly increasing the viscosity or if the carrier has evaporated through not being sealed effectively in the container you will also experience the same result.

Product was new in a sealed container. I did shake the container for a long time (~5min) noting that it had thick lumps in it. The liquid was at 20°, and it was a sunny day around 20°.


Having found that rust is the main problem with the lower spindle bearings, I have purchased a pack of 10 Chinese ABEC-3 6203-2RS bearings for $25 as spares for future replacement, it seems there is little benefit in using expensive high quality bearings… corrosion of the bearings is an inevitable part of washing the grass from under the deck. The alternative of  waterless cleaning of the underside of the deck would essentially require removal of the deck every mowing when the grass is wet and thick… not an attractive option, just replace the bearings periodically.

I note that the spindle assemblies used on commercial grade mowers are quite different to these, the lower bearings are much better protected from water ingress.

At next deck service, I may run a couple of beads of hardfacing on the rub points on the deck, they have worn a little.

The Steel-seal was not sprayable, but for this job brush application worked well. It is mid-autumn, next time I should do this in the hotter moths for quicker drying of the Steel-seal.