04/06/2011
It's fantastic to hear you've got your Honda TRX 400EX up and running with 3 1/4 litres of oil – that's the correct capacity, so you're on the right track there. However, the symptoms you're describing, particularly the revving up and losing momentum when cold, followed by improvement after a few throttle blips, strongly suggest a clutch slipping issue. While a change in oil viscosity can sometimes influence clutch behaviour, it's unlikely to be the sole cause of this particular problem. Let's delve deeper into potential causes and solutions.
Understanding the Cold Start Problem
The behaviour you're experiencing is often linked to the engine and clutch components being at their coldest. When you blip the throttle and the issue momentarily resolves, it indicates that the clutch plates might be sticking together when cold, or there's a slight variance in the clutch engagement that gets corrected by the increased engine speed and centrifugal force. The fact that it clears itself after a few 'wot' (wide-open throttle) applications points towards a temporary adhesion or a minor misalignment that re-establishes itself under load.
Clutch Slippage: The Likely Culprit
A clutch that slips will allow the engine RPMs to increase without a corresponding increase in wheel speed. This is exactly what you're describing. Several factors can contribute to clutch slippage, especially when cold:
- Worn Clutch Plates: Over time, the friction material on the clutch plates wears down. When this happens, the plates can't grip each other effectively, leading to slippage. This is more noticeable when the engine is cold and the oil is thicker.
- Incorrect Clutch Adjustment: The clutch cable or hydraulic system needs to be adjusted correctly. If there's too much free play, the clutch might not be fully engaging when cold. Conversely, if it's too tight, it could be slightly dragging, which might be exacerbated when cold.
- Contaminated Clutch Plates: Oil contamination, especially with certain types of additives or if the wrong oil is used (though 0W-30 is generally acceptable for many ATVs, it's always best to consult your owner's manual for the specific Honda recommendation), can reduce the friction between the clutch plates.
- Weak Clutch Springs: The springs that press the clutch plates together can lose their tension over time. If they are too weak, they won't provide enough clamping force, especially under initial load.
- Clutch Basket or Hub Damage: Grooves or wear on the clutch basket or hub can prevent the plates from engaging smoothly and fully.
Addressing the Cold Start Issue
Given your description, here’s a systematic approach to diagnose and resolve the cold start problem:
1. Clutch Adjustment
This is the easiest and cheapest thing to check. Refer to your Honda TRX 400EX owner's manual for the precise procedure. Generally, you’ll be looking for a specific amount of free play in the clutch lever. Too much play means the clutch isn't fully engaging; too little means it might be dragging.
2. Inspect Clutch Components
If the adjustment doesn't resolve the issue, the next step is to inspect the clutch itself. This involves removing the clutch cover.
What to look for:
- Clutch Plates: Examine the friction material on the clutch plates. If it's thin, glazed, or has burnt spots, they need replacing. Measure their thickness against the service limit specified in your manual.
- Steel Plates: Check the steel plates for bluing or warping, which indicates overheating.
- Clutch Springs: Measure the length of the clutch springs. If they are shorter than the service limit, they need replacing.
- Clutch Basket and Hub: Inspect the teeth on the clutch basket and hub for excessive wear or deep grooves.
3. Oil Considerations
While you've switched to 0W-30, it's crucial to ensure it meets the specifications for your TRX 400EX. Some oils, particularly those with high friction modifiers, can sometimes affect wet clutch performance. Always use an oil that is specifically rated for motorcycles or ATVs with wet clutches. JASO MA or MA2 ratings are generally good indicators. If your manual specifies a different viscosity or type, consider reverting to that.
Table: Oil Viscosity and Clutch Performance
| Viscosity Grade | Potential Clutch Impact (General) | Common ATV/Motorcycle Use |
|---|---|---|
| 0W-30 | Can be very thin when cold, potentially leading to less initial grip if not formulated for wet clutches. | Used in many modern vehicles, but always check manual for ATV compatibility. |
| 10W-40 | A common and generally safe viscosity for many wet clutches, offering a good balance of cold flow and protection. | Very common in ATVs and motorcycles. |
| 20W-50 | Thicker when hot, can provide better protection in high-temperature, high-load conditions. Might be slightly harder on cold starts. | Often used in older bikes or high-performance/heavy-duty applications. |
Important Note: Always consult your Honda TRX 400EX owner's manual for the recommended oil specifications. Using the wrong oil can lead to significant mechanical issues.
4. Engine Temperature and Oil Flow
It's possible that when cold, the oil isn't circulating optimally to the clutch components, or the oil is too thick to allow immediate proper engagement. As the engine warms up, the oil thins, and the clutch components expand slightly, which can temporarily alleviate the slipping. This reinforces the idea that the issue might be more pronounced when the entire drivetrain is cold.
Heated Grips and CDI Launch
It's great that you've got the Oxford heated grips sorted – they make a massive difference on colder rides! Enjoy those warm hands on your commute. And keeping an eye on the Dynatec CDI launch is exciting; performance upgrades can certainly enhance the riding experience.
Summary of Potential Causes for Slipping
Based on your description, the most probable causes for the revving and loss of momentum when cold are related to the clutch:
- Worn clutch plates
- Incorrect clutch adjustment
- Weak clutch springs
- Oil that may not be ideal for wet clutch performance (though 0W-30 is often acceptable, verify manual)
Frequently Asked Questions (FAQ)
Q1: How much oil does a Honda TRX 400EX take?
A1: The Honda TRX 400EX typically takes 3.2 litres (3 1/4 US quarts) of oil when the engine is dry, and approximately 2.9 litres (3 US quarts) when changing the oil and filter. You've confirmed 3 1/4 litres is correct, which is good.
Q2: Could the 0W-30 oil be causing my clutch to slip?
A2: While it's less common, some oils with specific additive packages can affect wet clutch performance. It's always best to use an oil explicitly rated for wet clutches (JASO MA/MA2) and to check your owner's manual for the recommended viscosity. If the issue persists after checking other clutch components, consider trying a different, recommended oil.
Q3: What are the symptoms of a slipping clutch on a TRX 400EX?
A3: The primary symptom is the engine revving up, but the ATV not accelerating proportionally. You might also notice a lack of power, especially when accelerating hard or going uphill. The feeling you described – revving up and losing momentum – is a classic sign.
Q4: How often should I check my clutch?
A4: It's good practice to check your clutch adjustment periodically, perhaps every few thousand miles or as part of your regular maintenance checks. If you notice symptoms of slipping, it should be inspected sooner.
Q5: Is it safe to ride with a slipping clutch?
A5: Riding with a slipping clutch is not recommended. It can cause further damage to the clutch plates, potentially leading to more expensive repairs. It also compromises your ability to accelerate and control the ATV effectively.
Hopefully, this gives you a clear direction to tackle the problem. Focus on the clutch first, as the symptoms are highly indicative of a clutch-related issue, particularly when cold. Good luck, and happy riding!
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