A loss of performance or difficulty starting your Suzuki GSX600f Katana could be caused by a problem in one or both of your motorcycle's ignition coils. Each coil consists of a wire winding that is connected by a pair of cables to two of the four spark plugs used by your Katana. A damaged winding or cable will weaken the final output to the spark plug, leading to starting and performance problems. You can check the ignition coils by verifying that the coil is generating a spark, and by testing the physical condition of the coil's windings and cables.
Remove the upper and side fairings, using a 4mm Allen wrench to unscrew the fairing bolts. Unlock and remove the rider's seat, using the ignition key.
Pull the fuel lines off of the fuel valve under the left side of the fuel tank. Unscrew the pair of bolts from the base of the fuel tank, using a 10mm socket. Pull the fuel tank to the rear of the motorcycle to remove it..
Pull the cables off of the two spark plugs on the right side of the motor. The spark plug cable furthest to the right is connected to the right ignition coil, while the second cable is connected to the left ignition coil. Unscrew the spark plugs from the motor, using a spark plug socket. Plug the ignition cables back onto the removed spark plugs.
Hold the spark plugs against the motor and start the motorcycle for a few seconds. Observe the gap between the electrode at the tip of both spark plugs for spark. Ideally, the spark should have a bright, blue appearance.
Replace the spark plugs with new DR8E spark plugs, if no spark is present. Repeat the test. Replace the corresponding ignition coil if there is still no spark present at the spark plugs' electrodes.
Proceed to Section 2 for further diagnosis, or reassemble the motorcycle following the reverse method of removal.
Remove the suspect ignition coil from the motorcycle's frame, using a 10mm socket. Unplug the coil's cables from the remaining spark plug in the motor and from the spark plug removed in Section 1. Unplug the motorcycle's wiring harness connector from the back of the ignition coil. Remove the remaining ignition coil, if needed, using the same procedure.
Set your multimeter to read an R X 1 resistance range, using the meter's settings dial.
Measure the ignition coil's primary winding at the terminal that connects to the motorcycle's wiring harness, using your multimeter. Touch the meter's red probe to the coil's positive (+) terminal and the black probe to the coil's negative (-) terminal. Take note of the measurement on the meter's display. Replace the ignition coil if its primary winding has a resistance measurement less than 3 ohms or greater than 5 ohms.
Set your multimeter to read an R X 1,000 resistance range, using the meter's settings dial.
Measure the ignition coil's spark plug cables, using your multimeter. Touch the meter's probes to the metal connectors within the cable's end caps. Take note of the resistance measurement on the meter's display, indicated in ohms. Replace the ignition coil if the cables have a resistance measurement less than 25,000 ohms or greater than 45,000 ohms.
Reinstall the ignition coil if its primary winding and spark plug cables are within the specified resistance range, using the reverse method of removal. Replace the entire ignition coil if either the primary winding or the spark plug cables are within specification, as the ignition coil and its cables are a combined assembly.
Reassemble the motorcycle following the reverse method of removal. Connect the left ignition coil's cables to the pair of spark plugs in the middle of the motor's cylinder (#2 and #3), while the right coil's cable connect to the spark plugs on the sides of the cylinder (#1 and #4).
Testing should be performed at a minimum room temperature of 68F. If the room temperature is cooler than that, warm up the motorcycle by letting it idle for three minutes, Detailed disassembly and troubleshooting information can be found in a Suzuki factory service manual.