Testing Ignition Coils: Resistance Specifications for Yamaha XJ Models

Diagnosing ignition problems in Yamaha XJ motorcycles often requires a methodical approach, and testing the ignition coils and related components is a crucial step. Resistance testing is a straightforward method to assess the health of your ignition system’s electrical components. This guide provides the resistance specifications for various components within the ignition systems of different Yamaha XJ models, including pick-up coils, ignition coils, spark plug caps, and spark plugs.

Understanding these specifications is essential for accurate troubleshooting. By comparing your component readings against the factory values, you can pinpoint whether a part is functioning within its acceptable range or needs replacement. This detailed information will help ensure your XJ motorcycle runs smoothly and efficiently.

Below are the resistance specifications organized by Yamaha XJ model. Remember that “K” denotes thousands of ohms (Ω), so 5K ohms equals 5,000 ohms.

XJ550 Models

• Pick-up Coils: 650 ohms +/- 20% (Acceptable range: 520 ohms to 780 ohms)
• Ignition Coils:
  • Primary side: 2.5 ohms +/- 10% (Acceptable range: 2.25 ohms – 2.75 ohms)
  • Secondary side (without spark plug caps): 11K ohms +/- 20% (Acceptable range: 8,800 ohms – 13,200 ohms)
• Spark Plug Caps: 10K ohms +/- 20% per cap (Acceptable range: 8,000 to 12,000 ohms per cap)
• Spark Plugs: 0 ohms per plug

XJ650 Models

• Pick-up Coils:
  • 1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% (Acceptable range: 560 ohms to 840 ohms)
  • 1982 XJ650RJ Seca (non-YICS engines): 700 ohms +/- 20% (Acceptable range: 560 ohms to 840 ohms)
  • 1982-84 XJ650 Maxim: 650 ohms +/- 20% (Acceptable range: 520 ohms to 780 ohms)
  • 1982 XJ650RJC Seca (YICS engine): 650 ohms +/- 20% (Acceptable range: 520 ohms to 780 ohms)
  • 1982-83 XJ650 Turbo: 120 ohms +/- 20% (Acceptable range: 96 ohms to 144 ohms)
• Ignition Coils:
  • Primary side: 2.5 ohms +/- 10% (Acceptable range: 2.25 ohms – 2.75 ohms)
  • Secondary side (without spark plug caps): 11K ohms +/- 20% (Acceptable range: 8,800 ohms – 13,200 ohms)
• Spark Plug Caps: 5K ohms +/- 20% per cap (Acceptable range: 4,000 to 6,000 ohms per cap)
• Spark Plugs: 0 ohms per plug

XJ700 Air-Cooled Models

• Pick-up Coils: 120 ohms +/- 20% (Acceptable range: 96 ohms to 144 ohms)
• Ignition Coils:
  • Primary side: 2.7 ohms +/- 10% (Acceptable range: 2.43 ohms – 2.97 ohms)
  • Secondary side (without spark plug caps): 12K ohms +/- 20% (Acceptable range: 9,600 ohms – 14,400 ohms)
• Spark Plug Caps:
  • 1985 N/NC models: 5K ohms +/- 20% (Acceptable range: 4,000 to 6,000 ohms per cap)
  • 1986 S/SC models: 10K ohms +/- 20% (Acceptable range: 8,000 to 12,000 ohms per cap)
• Spark Plugs:
  • 1985 N/NC models: 0 ohms per plug
  • 1986 S/SC models: 5K ohms per plug

XJ700 Water-Cooled Models

• Pick-up Coils: 120 ohms +/- 20% (Acceptable range: 96 ohms to 144 ohms)
• Ignition Coils:
  • Primary side: 2.7 ohms +/- 10% (Acceptable range: 2.43 ohms – 2.97 ohms)
  • Secondary side (without spark plug caps): 12K ohms +/- 20% (Acceptable range: 9,600 ohms – 14,400 ohms)
• Spark Plug Caps: 10K ohms +/- 20% per cap (Acceptable range: 8,000 to 12,000 ohms per cap)
• Spark Plugs:
  • 1985 XN/XNC models: 0 ohms per plug
  • 1986 SX/SXC models: 5K ohms per plug

XJ750 Air-Cooled Models

• Pick-up Coils: 650 ohms +/- 20% (Acceptable range: 520 ohms to 780 ohms)
• Ignition Coils:
  • Primary side: 2.5 ohms +/- 10% (Acceptable range: 2.25 ohms – 2.75 ohms)
  • Secondary side (without spark plug caps): 11K ohms +/- 20% (Acceptable range: 8,800 ohms – 13,200 ohms)
• Spark Plug Caps:
  • 1981-83 models: 5K ohms +/- 20% (Acceptable range: 4,000 to 6,000 ohms per cap)
  • 1984 RL models: 10K ohms +/- 20% (Acceptable range: 8,000 to 12,000 ohms per cap)
• Spark Plugs: 0 ohms per plug

XJ750 Water-Cooled Models

• Pick-up Coils: 120 ohms +/- 20% (Acceptable range: 96 ohms to 144 ohms)
• Ignition Coils:
  • Primary side: 2.7 ohms +/- 10% (Acceptable range: 2.43 ohms – 2.97 ohms)
  • Secondary side (without spark plug caps): 12K ohms +/- 20% (Acceptable range: 9,600 ohms – 14,400 ohms)
• Spark Plug Caps: 15K ohms +/- 20% per cap (Acceptable range: 12,000 to 18,000 ohms per cap)
• Spark Plugs: 5K ohms per plug

XJ900RK, RL, N, FN, and F Models

• Pick-up Coils: 120 ohms +/- 20% (Acceptable range: 96 ohms to 144 ohms)
• Ignition Coils:
  • Primary side:
    • Original coils, marked CM12-20: 2.7 ohms +/- 10% (Acceptable range: 2.43 ohms – 2.97 ohms)
    • Replacement coils, marked CM12-09 or CM12-10: 2.5 ohms +/- 10% (Acceptable range: 2.25 ohms – 2.75 ohms)
  • Secondary side (without spark plug caps):
    • Original coils, marked CM12-20: 13.2K ohms +/- 20% (Acceptable range: 10,560 ohms – 15,840 ohms)
    • Replacement coils, marked CM12-09 or CM12-10: 11K ohms +/- 20% (Acceptable range: 8,800 ohms – 13,200 ohms)
• Spark Plug Caps:
  • RK and RL models: 5K ohms +/- 20% (Acceptable range: 4,000 to 6,000 ohms per cap)
  • N, FN, and F models: 10K ohms +/- 20% (Acceptable range: 8,000 to 12,000 ohms per cap)
  • S and SH models: 15K ohms +/- 20% (Acceptable range: 12,000 to 18,000 ohms per cap)
• Spark Plugs:
  • RK and RL models: 0 ohms per plug
  • N, FN, and F models: 5K ohms per plug

XJ1100 Models

• Pick-up Coils: 120 ohms +/- 20% (Acceptable range: 96 ohms to 144 ohms)
• Ignition Coils:
  • Primary side: 2.5 ohms +/- 10% (Acceptable range: 2.25 ohms – 2.75 ohms)
  • Secondary side (without spark plug caps): 11K ohms +/- 20% (Acceptable range: 8,800 ohms – 13,200 ohms)
• Spark Plug Caps: 5K ohms +/- 20% per cap (Acceptable range: 4,000 to 6,000 ohms per cap)
• Spark Plugs: 0 ohms per plug

Important Notes on Testing Coils:

• Pick-up Coil Testing: For pick-up coils, on many XJ models, you can check resistance at their connector to the TCI box. Measure between the grey and black wire for one coil and between the orange and black wire for the other. The orange wire typically triggers coils for cylinders #1 and #4, while the grey wire triggers coils for cylinders #2 and #3.
• Ignition Coil Wiring: The ignition coil for cylinders #1/#4 is often located on the left side and typically has a solid orange (ground) wire and a red-with-white-tracer-stripe (hot) wire. The coil for cylinders #2/#3 is often on the right side with a solid grey (ground) wire and a red-with-white-tracer-stripe (hot) wire. Always refer to your specific model’s wiring diagram for confirmation.
• Testing Procedure: When testing secondary ignition coil resistance, always remove the spark plug caps. Test the caps separately to isolate potential issues. This method allows you to determine if the problem lies within the coils, caps, or both.

By using these resistance specifications and following proper testing procedures, you can effectively diagnose ignition system problems in your Yamaha XJ motorcycle and ensure optimal performance.