The Yamaha XS750, a triple-cylinder motorcycle produced from 1976 to 1979 (and continuing as the XS850 until 1981), holds a special place in motorcycling history. Its unique engine configuration offered a distinctive sound and smooth power delivery, making it a popular choice for touring and everyday riding. However, like any classic motorcycle, the XS750 is prone to certain problems as it ages. Understanding these common issues is crucial for owners looking to maintain, restore, or simply keep their beloved triple running smoothly.

So, You've Got an XS750? Let's Talk About the Quirks

Owning a vintage motorcycle is a rewarding experience, but it comes with its own set of challenges. The XS750 is no exception. While it's a robust machine, years of use (and sometimes neglect) can lead to problems that need addressing. Knowing what to look for can save you time, money, and frustration.

The Dreaded Second Gear: A Weak Spot

One of the most widely known and discussed issues with the XS750 is its second gear failure. This is a fairly common problem, particularly on earlier models.

  • The Cause: The second gear is often subjected to significant stress during acceleration and shifting. Over time, the gear teeth can become worn or even break, leading to slipping, grinding, or complete gear failure. Harsh shifting habits exacerbate this issue.
  • Symptoms: You might notice the bike jumping out of second gear, difficulty engaging second gear, or a grinding noise when in second. Sometimes, there's a distinct "clunk" when shifting into second.
  • The Fix: Unfortunately, the only real solution is to replace the second gear. This requires splitting the engine cases, a complex and time-consuming job best left to experienced mechanics. Finding good used gears can be a challenge, and new old stock (NOS) parts are increasingly rare and expensive. Consider upgrading to a stronger aftermarket gear if available.

Carburetor Chaos: Keeping Those Triple Carbs in Sync

The XS750 uses a bank of three Mikuni carburetors. These carbs are essential for delivering the correct air-fuel mixture to each cylinder, ensuring smooth running and optimal performance. However, they are also a common source of problems.

  • Synchronization Issues: The three carbs need to be perfectly synchronized to ensure each cylinder is firing evenly. Over time, the synchronization can drift, leading to uneven idle, poor throttle response, and reduced power.
  • Cleaning and Rebuilding: Carburetors can become clogged with dirt, varnish, and other debris, especially if the bike has been sitting for a long time. This can restrict fuel flow and cause the engine to run poorly. A thorough cleaning and rebuild, including replacing worn jets and gaskets, is often necessary.
  • Vacuum Leaks: Vacuum leaks around the carburetors or intake manifolds can disrupt the air-fuel mixture, leading to similar symptoms as synchronization problems. Check all hoses and connections for cracks or looseness.
  • The Fix: Invest in a good carburetor synchronizer tool (vacuum gauges) and learn how to use it. Regular carburetor cleaning and maintenance are essential. Consider replacing old rubber parts, like intake manifolds, to prevent vacuum leaks.

TCI Troubles: When the Ignition Fails

The Transistor Controlled Ignition (TCI) system is responsible for sparking the engine and keeping it running. While generally reliable, the TCI unit can fail, leading to a complete loss of spark or intermittent ignition problems.

  • The Cause: The TCI unit is an electronic component and can be susceptible to heat, vibration, and age-related degradation. Internal components can fail, leading to erratic or non-existent spark.
  • Symptoms: The bike may refuse to start, run poorly, or stall unexpectedly. You might also experience misfires or a lack of power.
  • The Fix: Testing the TCI unit requires specialized equipment and knowledge. If you suspect a faulty TCI, consult a qualified mechanic. Replacement TCI units are available, but can be expensive. Some owners opt for aftermarket electronic ignition systems for improved reliability and performance.

Charging System Conundrums: Keeping the Battery Happy

The charging system, consisting of the alternator, rectifier/regulator, and battery, is crucial for keeping the battery charged and powering the bike's electrical components. Problems with the charging system can lead to a dead battery and other electrical issues.

  • Alternator Issues: The alternator generates electricity to charge the battery. Over time, the stator windings can short out or the rotor magnets can weaken, reducing the alternator's output.
  • Rectifier/Regulator Failure: The rectifier/regulator converts AC voltage from the alternator to DC voltage and regulates the voltage to prevent overcharging the battery. A faulty rectifier/regulator can either undercharge or overcharge the battery, leading to damage.
  • Battery Problems: Batteries have a limited lifespan and will eventually need to be replaced. Old or poorly maintained batteries can lose their ability to hold a charge, causing starting problems and other electrical issues.
  • The Fix: Use a multimeter to test the alternator output and the rectifier/regulator voltage. Replace any faulty components. Ensure the battery is properly maintained and replaced as needed. Check all wiring connections for corrosion or damage.

Shaft Drive Woes: Maintaining the Drivetrain

The XS750 utilizes a shaft drive system, which is generally more reliable than a chain drive. However, it still requires maintenance to prevent problems.

  • U-Joint Issues: The U-joints in the driveshaft can wear out over time, leading to vibration and noise.
  • Final Drive Problems: The final drive unit contains gears and bearings that can wear out or become damaged. Low oil levels or contaminated oil can accelerate wear.
  • The Fix: Regularly check the U-joints for play and lubricate them as needed. Change the final drive oil according to the manufacturer's recommendations. Inspect the final drive unit for leaks or unusual noises. Rebuilding the final drive can be a complex job, requiring specialized tools and knowledge.

Rust Never Sleeps: Dealing with Corrosion

Like any motorcycle of its age, the XS750 is susceptible to rust. Rust can affect various parts of the bike, including the fuel tank, frame, and exhaust system.

  • Fuel Tank Rust: Rust inside the fuel tank can clog the fuel filter and carburetors, leading to poor performance.
  • Frame Rust: Rust on the frame can weaken its structural integrity, making the bike unsafe to ride.
  • Exhaust System Rust: Rust on the exhaust system can cause leaks and reduce its effectiveness.
  • The Fix: Treat rust in the fuel tank with a rust remover or liner. Repair or replace rusted frame sections. Replace rusted exhaust components. Prevent rust by storing the bike in a dry environment and applying rust inhibitors.

Electrical Gremlins: Chasing Down Shorts and Bad Connections

Old motorcycles are notorious for electrical problems. The XS750 is no exception.

  • Wiring Harness Issues: The wiring harness can become brittle and cracked over time, leading to shorts and open circuits.
  • Bad Connections: Corrosion and loose connections can disrupt electrical flow, causing various problems.
  • The Fix: Inspect the wiring harness for damage and repair or replace as needed. Clean and tighten all electrical connections. Use dielectric grease to prevent corrosion.

Frequently Asked Questions

  • Why is my XS750 hard to start? Several factors can contribute, including a weak battery, clogged carburetors, or a faulty ignition system. Start by checking the basics: battery voltage, fuel flow, and spark.
  • My XS750 is running rough. What could be the cause? Common causes include unsynchronized carburetors, vacuum leaks, or a faulty ignition system. A compression test can also help identify engine problems.
  • How often should I change the oil on my XS750? Change the oil and filter every 3,000 miles or annually, whichever comes first. Use a high-quality motorcycle oil designed for wet clutches.
  • Where can I find parts for my XS750? Many online retailers specialize in vintage motorcycle parts. You can also check eBay and motorcycle forums for used parts.
  • Is the XS750 a reliable motorcycle? When properly maintained, the XS750 can be a reliable motorcycle. However, its age means that regular maintenance and repairs are necessary.

The Bottom Line

The Yamaha XS750 is a classic motorcycle with its own set of quirks. By understanding the common problems and taking proactive steps to maintain your bike, you can keep it running smoothly and enjoy the unique experience of owning a vintage triple. Addressing issues like second gear failure, carburetor synchronization, and electrical problems will ensure many more miles of enjoyable riding.