Kuhn Hay Mower Maintenance & Common Issues

Hay mowers are essential pieces of equipment for any agricultural operation that deals with forage. Kuhn is a well-respected manufacturer in this field, known for producing robust and reliable machinery. However, like all mechanical devices, Kuhn hay mowers require regular maintenance and can sometimes present specific issues that owners need to address. This article delves into some common questions and concerns raised by owners of Kuhn hay mowers, focusing on models like the GMD 600 and 800 series, covering aspects such as heavy-duty components, gearbox lubrication, and drive system repairs.

Understanding Heavy-Duty (HD) Hats on Kuhn GMD 600 Mowers

A common point of discussion among Kuhn GMD 600 owners revolves around the presence of 'heavy-duty (HD) hats'. While the provided text doesn't explicitly detail what constitutes an HD hat in a technical sense, it implies that these are a desirable feature, present on one mower and potentially absent on another, even if the models are otherwise similar (aside from paint colour and tarp). In the context of agricultural machinery, 'heavy-duty' components typically refer to parts designed to withstand greater stress, wear, and tear, often featuring enhanced materials or construction. For hay mowers, HD hats could relate to the protective caps or covers on crucial rotating parts of the cutter bar or drive system, designed for increased durability and protection against impacts or debris.

The anecdotal evidence suggests that the presence of HD hats might be a differentiating factor between seemingly identical mowers, possibly impacting longevity and resistance to damage. If you are considering a Kuhn GMD 600 or similar model, inquiring about the specifications of the 'hats' or protective coverings on the cutter bar units could be beneficial. While the original query doesn't provide a definitive answer, it highlights the importance of understanding the specific build of your machinery. Often, manufacturers offer different specifications or upgrade options, and identifying these can lead to a more robust and reliable machine.

Gearbox and Cutterbar Oil: Separation and Drainage Concerns

One of the more perplexing issues for a Kuhn GMD 600 owner involved the observation of gearbox oil draining from the cutterbar when both were filled. The user drained both the cutterbar and the gearbox, refilled the cutterbar, and noticed the new oil escaping from the gearbox drain plug. This leads to a crucial question: are the gearbox and cutterbar oil systems in a Kuhn GMD 600 separated by a seal?

In many agricultural mowers, the cutterbar and the main gearbox are indeed separate lubrication systems. The cutterbar itself often contains multiple smaller gearboxes, one for each cutting disc, which require their own specific lubrication. The main gearbox, typically located at the front of the mower where the PTO shaft connects, drives the entire cutterbar assembly. If oil is observed migrating between these systems, it strongly suggests a failure of the seal that is meant to keep them separate. This could be a seal between the main gearbox output shaft and the input to the cutterbar drive mechanism, or potentially internal seals within the cutterbar drive itself.

Why Oil Might Migrate Between Systems

Several factors could lead to oil migration:

• Seal Failure: The most common reason is a worn, damaged, or improperly seated seal. Over time, seals can degrade due to age, heat, or contamination.
• Overfilling: If one system is overfilled, the excess pressure can force oil past a seal into the adjacent system.
• Improper Assembly: If the mower has been serviced previously, a seal might not have been installed correctly.
• Component Wear: Excessive wear on shafts or housing bores can compromise the effectiveness of even a good seal.

The fact that the user noticed new oil draining from the gearbox plug after refilling the cutterbar strongly indicates a breach in the sealing between these two components. It is generally not considered normal for oil to freely drain from one system into another under these circumstances. Addressing this issue promptly is important to prevent lubrication failure in either the gearbox or the cutterbar, which could lead to significant damage.

DIY vs. Dealer Repair: Drive Pulley Bearing on Kuhn GMD 600

Another significant issue encountered was a burned belt smell followed by the discovery of an out-of-alignment drive pulley with a failed bearing on the drive shaft of a Kuhn mower. This brings up the practical question of whether this is a manageable DIY project or if it warrants professional attention from a dealer.

Repairing a failed drive pulley bearing on a hay mower can range in difficulty depending on the specific design of the mower and the accessibility of the component. Here's a breakdown to help assess the situation:

Assessing the DIY Feasibility

DIY Pointers and Potential Pitfalls

If you decide to tackle this yourself, here are some pointers:

• Identify the Bearing: Carefully note the part number stamped on the old bearing. If it's unreadable, measure its dimensions (inner diameter, outer diameter, width) and consult a bearing supplier.
• Use Proper Tools: A hydraulic press is often the best tool for removing and installing bearings. If a press isn't available, a carefully executed hammer-and-drift method can work, but the risk of damaging the shaft or bearing seat is higher. Always use a bearing puller specifically designed for the task.
• Cleanliness is Crucial: Ensure the shaft, bearing housing, and new bearing are meticulously clean before installation. Contamination can ruin a new bearing quickly.
• Proper Installation: When pressing a bearing, ensure it goes on straight. Force should be applied to the outer race when installing onto a shaft, and to the inner race when installing into a housing. For this scenario, it's likely pressing onto a shaft, so force on the outer race is key.
• Check Alignment: After replacing the bearing, double-check that the pulley is correctly aligned on the shaft. Misalignment is often the cause of bearing failure in the first place, and it's critical to correct it. Check the pulley itself for any damage or warping.
• Reassemble Carefully: Reinstall guards and covers, ensuring no wires or hoses are pinched.

What NOT to do: Avoid using excessive force, hammering directly on the bearing, or forcing the pulley onto a dirty or damaged shaft. Never try to reuse a bearing that has failed; it's meant to be replaced.

The decision between DIY and dealer largely depends on your comfort level with mechanical repairs, the availability of the right tools, and the complexity of accessing the drive shaft. For many, the peace of mind and expertise offered by a dealer might be worth the cost, especially if the mower is critical to their operation.

Kuhn 800 Series Lubrication: Synthetic Gear Oil?

Regarding the Kuhn 800 series, a user inquired about the use of synthetic gear oil. The response indicated that the user had been using conventional gear oil, changing it every 200 hours as recommended by the manual, and had experienced no issues. This suggests that for the Kuhn 800, conventional, high-quality gear oil that meets the manufacturer's specifications is perfectly adequate and effective.

While synthetic oils often offer benefits like improved thermal stability and extended drain intervals, they are not always a mandatory requirement, especially if the manufacturer's recommendations are met with conventional oils. The key takeaway here is adherence to the owner's manual specifications for oil type and change intervals. If the manual specifies a particular API (American Petroleum Institute) service classification or viscosity grade (e.g., SAE 90), using a conventional oil that meets these standards is likely sufficient. Always consult your specific Kuhn 800 owner's manual for the most accurate lubrication recommendations.

The Importance of Owner's Manuals

Owner's manuals are invaluable resources. They provide manufacturer-specific guidance on:

• Recommended lubricant types and specifications.
• Fluid capacities for gearboxes and hydraulic systems.
• Maintenance schedules (e.g., oil change intervals, greasing points).
• Troubleshooting common issues.
• Safety precautions.

For any Kuhn hay mower, referring to the specific model's owner's manual is the most reliable way to ensure proper maintenance and care, maximising the lifespan and performance of the equipment.

Hitching and Unhitching Kuhn Mowers

A brief mention was made about the difficulty of hitching and unhitching mowers, with one user finding a solution by using adapters for hitch pins and a quick hitch system. This highlights a practical, everyday challenge for many farmers. While not a mechanical failure, ease of use and efficient field preparation are crucial. Investing in a quick hitch system can significantly reduce the time and effort required to connect and disconnect implements, improving overall workflow and reducing operator fatigue.

Tips for Easier Hitching

• Quick Hitches: As mentioned, these are designed to simplify implement attachment.
• Hitch Pin Adapters: These can help if the mower's hitch points are not perfectly compatible with standard quick hitch categories.
• Level Ground: Always try to hitch on level, firm ground.
• Proper Alignment: Ensure the tractor's drawbar or quick hitch is aligned correctly with the mower's hitch before attempting to connect.

While the technical aspects of hay mower maintenance are vital, the practicalities of operation, such as hitching, also contribute to the overall user experience and efficiency of the machinery.

In conclusion, maintaining Kuhn hay mowers involves understanding specific components like HD hats, ensuring proper lubrication systems are sealed, and knowing when to tackle repairs yourself or seek professional help. Always rely on your owner's manual and prioritize cleanliness and correct procedures for any maintenance task.