The Suzuki Eiger 400, a workhorse ATV known for its reliability, can sometimes stumble over a seemingly small component: the petcock. This little valve, responsible for controlling the fuel flow from the tank to the carburetor, can cause a surprising amount of frustration when it malfunctions. Understanding the common issues with the Eiger 400's petcock, along with knowing how to diagnose and fix them, can save you time, money, and a lot of headaches on the trail or in the field.

What Exactly Is a Petcock, Anyway?

Let's break down what a petcock does and why it's so important. Think of it as the fuel tank's gatekeeper. It's a valve, usually located at the bottom of the fuel tank, that controls the flow of gasoline to the engine. On the Eiger 400, it typically has three positions:

  • ON: Fuel flows normally to the carburetor. This is your standard operating position.
  • RES (Reserve): Allows you to access the bottom portion of the tank when the main fuel supply is low. Essentially, it gives you a little extra range when you're running on fumes.
  • PRI (Prime): Bypasses the vacuum-operated system (more on that later) and allows fuel to flow directly to the carburetor, useful for starting after the ATV has been sitting for a while or if the carburetor has run dry.

Without a properly functioning petcock, your Eiger 400 simply won't run – or, at best, will run poorly.

The Usual Suspects: Common Eiger 400 Petcock Problems

Now, let's dive into the issues that commonly plague the Eiger 400's petcock. These problems can manifest in various ways, from difficulty starting to poor performance and even fuel leaks.

  • Clogged Fuel Filter/Screen: This is probably the most frequent culprit. The petcock has a small filter screen inside the tank to prevent debris from entering the fuel line. Over time, this screen can become clogged with rust, sediment, and other contaminants, restricting fuel flow.
  • Vacuum Line Issues: The Eiger 400 (and many other ATVs) uses a vacuum-operated petcock. This means that the petcock only allows fuel to flow when the engine is running and creating vacuum. A cracked, disconnected, or otherwise compromised vacuum line will prevent the petcock from opening, starving the engine of fuel.
  • Diaphragm Failure: Inside the petcock, there's a rubber diaphragm that responds to the vacuum signal. Over time, this diaphragm can crack, tear, or become stiff, preventing it from functioning correctly. This is a common cause of fuel starvation or fuel leaks.
  • Sticking or Corroded Valve: The internal valve mechanism can become sticky or corroded due to old fuel, moisture, or simply age. This can prevent the petcock from switching between positions smoothly or from sealing properly.
  • Leaking Petcock: This is a clear sign of a problem. Fuel leaking from the petcock itself, especially around the valve lever or the fuel line connections, indicates a worn-out seal, a cracked housing, or a damaged valve.

Diagnosing the Problem: Is it Really the Petcock?

Before you start tearing into your Eiger 400, it's crucial to confirm that the petcock is indeed the source of your woes. Here's a step-by-step approach to diagnosing petcock-related issues:

  1. Check the Fuel Level: Obvious, but important. Make sure you actually have fuel in the tank!
  2. Inspect the Fuel Lines: Look for any cracks, kinks, or leaks in the fuel lines running from the petcock to the carburetor. Replace any damaged lines.
  3. Examine the Vacuum Line: This is critical for vacuum-operated petcocks. Check the vacuum line that runs from the engine (usually the intake manifold) to the petcock. Make sure it's securely connected at both ends and that there are no cracks or signs of damage. A simple test is to disconnect the line at the petcock end (with the engine off!) and suck on it gently. You should feel a slight vacuum. If not, there's a leak in the line or the connection at the engine is bad.
  4. Test Fuel Flow: With the fuel line disconnected from the carburetor (but still attached to the petcock), place a container under the fuel line. Turn the petcock to the "ON" position. Fuel should flow freely. If it doesn't, try the "RES" position. If you still don't get fuel flow, try the "PRI" (Prime) position. If fuel flows in "PRI" but not in "ON" or "RES," it strongly suggests a vacuum-related problem or a clogged filter. If there's no flow in any position, the petcock is likely clogged or malfunctioning internally.
  5. Check for Leaks: Carefully inspect the petcock for any signs of fuel leakage. Pay close attention to the valve lever, the fuel line connections, and the body of the petcock itself.
  6. Listen for the Vacuum: With the engine running, and the petcock in the "ON" position, listen carefully near the petcock. You should hear a faint "click" or a change in sound as the vacuum pulls the valve open and allows fuel to flow. If you don't hear anything, the vacuum system might not be working.
  7. Bypass Test: As a last resort, you can try temporarily bypassing the petcock altogether. This involves directly connecting the fuel line from the fuel tank to the carburetor (using an appropriate adapter if necessary). This is for diagnostic purposes only and should not be done permanently. If the ATV runs normally with the petcock bypassed, it confirms that the petcock is the problem.

Important Note: Always exercise extreme caution when working with fuel. Work in a well-ventilated area, away from any sources of ignition, and have a fire extinguisher nearby.

Fixing the Problem: Repair or Replace?

Once you've confirmed that the petcock is the culprit, you have two main options: repair or replace.

  • Repair: In some cases, you can repair the petcock. This usually involves disassembling it, cleaning all the parts thoroughly, replacing any worn or damaged components (such as the diaphragm or O-rings), and reassembling it. Petcock repair kits are available for some models of the Eiger 400, but availability can vary.
  • Replace: If the petcock is severely damaged, corroded, or if you're not comfortable disassembling and repairing it, replacement is the better option. New aftermarket petcocks are readily available for the Eiger 400 at reasonable prices.

Here's a closer look at each option:

Repairing the Petcock:

  • Pros: Can be more economical than replacing the entire petcock, especially if only a few parts are damaged. Allows you to retain the original equipment.
  • Cons: Can be time-consuming and require some mechanical aptitude. Repair kits may not always be available or complete. There's no guarantee that the repair will be successful.

Replacing the Petcock:

  • Pros: Relatively quick and easy. Ensures that all components are new and in good working order. Provides a more reliable solution.
  • Cons: More expensive than repairing. Aftermarket petcocks may not always be of the same quality as the original equipment.

Steps for Cleaning a Petcock (If Repairing):

  1. Drain the Fuel Tank: Before you do anything, drain the fuel tank completely.
  2. Disconnect the Petcock: Disconnect the fuel lines and the vacuum line from the petcock.
  3. Remove the Petcock: Unscrew the petcock from the fuel tank.
  4. Disassemble the Petcock: Carefully disassemble the petcock, noting the order of the parts.
  5. Clean the Parts: Clean all the parts thoroughly with carburetor cleaner or a similar solvent. Pay special attention to the filter screen and any small passages. Use compressed air to blow out any remaining debris.
  6. Inspect the Parts: Inspect all the parts for wear, damage, or corrosion. Replace any parts that are questionable.
  7. Reassemble the Petcock: Reassemble the petcock in the reverse order of disassembly.
  8. Reinstall the Petcock: Reinstall the petcock on the fuel tank.
  9. Reconnect the Fuel Lines and Vacuum Line: Reconnect the fuel lines and the vacuum line.
  10. Test for Leaks: Fill the fuel tank and check for any leaks.

Steps for Replacing a Petcock:

  1. Drain the Fuel Tank: Before you do anything, drain the fuel tank completely.
  2. Disconnect the Petcock: Disconnect the fuel lines and the vacuum line from the old petcock.
  3. Remove the Old Petcock: Unscrew the old petcock from the fuel tank.
  4. Install the New Petcock: Screw the new petcock into the fuel tank. Be sure to use a new O-ring or gasket if one is required.
  5. Reconnect the Fuel Lines and Vacuum Line: Reconnect the fuel lines and the vacuum line.
  6. Test for Leaks: Fill the fuel tank and check for any leaks.

Prevention is Key: Keeping Your Petcock Healthy

Preventing petcock problems is far easier than dealing with them after they occur. Here are a few tips to keep your Eiger 400's petcock in good working order:

  • Use Fresh Fuel: Old fuel can break down and leave deposits that can clog the petcock.
  • Add Fuel Stabilizer: If you're storing your ATV for an extended period, add fuel stabilizer to the tank to prevent fuel degradation.
  • Clean the Fuel Tank Regularly: Periodically drain and clean the fuel tank to remove any sediment or debris that may have accumulated.
  • Inspect the Fuel Lines and Vacuum Line: Regularly inspect the fuel lines and vacuum line for cracks, leaks, or damage.
  • Consider an Inline Fuel Filter: Adding an inline fuel filter between the fuel tank and the petcock can provide an extra layer of protection against debris.

Frequently Asked Questions

  • Why is my Eiger 400 only running on "Prime"? This often indicates a vacuum leak or a faulty diaphragm in the petcock. The "Prime" setting bypasses the vacuum system.
  • How often should I replace my petcock? There's no set replacement interval. Replace it when it shows signs of failure, such as leaks or restricted fuel flow.
  • Can I use an aftermarket petcock? Yes, but choose a reputable brand and ensure it's designed for the Eiger 400.
  • Is it difficult to replace a petcock? No, it's a relatively simple task that most people can do with basic tools.
  • Why is fuel leaking from the vacuum line on my petcock? This usually indicates a ruptured diaphragm inside the petcock. The petcock needs to be replaced or rebuilt.

The Bottom Line

The Suzuki Eiger 400 petcock, while a small part, plays a crucial role in the ATV's overall performance. By understanding the common problems, knowing how to diagnose them, and following proper maintenance practices, you can keep your Eiger 400 running smoothly for years to come. Don't neglect this vital component – a little attention can go a long way!