Clean the Roller: Remove any grass clippings or debris that may have accumulated on the roller. Use a brush or compressed air to clean it thoroughly.

Inspect for Damage: Check the roller for any signs of wear, cracks, or other damage. If the roller is damaged, it may need to be replaced.

Lubricate Bearings: Most front rollers have bearings that require regular lubrication. Apply a suitable lubricant to the bearings to ensure smooth operation. Check the manufacturer’s recommendations for the type of lubricant to use.

Adjust the Roller: Ensure that the roller is properly aligned and adjusted. The roller should be level and evenly spaced relative to the reel blades. Misalignment can affect the cutting performance.

Check Roller Condition: Ensure the roller turns freely without excessive resistance. If it’s not turning smoothly, there may be a need for further maintenance or replacement of parts.

Reassemble and Test: After servicing, reassemble any parts you may have removed, and test the mower to ensure everything is working correctly.

Sound like the black goo is grease.

Cheers
Max.