Kawasaki Zephyr 750 Sputtering problem! [Archive] - Kawasaki Motorcycle Forums

Kawasaki Zephyr 750 Sputtering problem!

05-25-2012, 01:06 AM
Bike runs great no problems but one, when I decide to unleash the power, SOMETIMES it sputters, has to catch up then it unleashes the fury. Any clue what it is? Much research says all I have to do is give it some sea foam. So i put 3 gallons in gave it some sea foam. Not much. Didn't measure but something. Lets see if this works. Any help would he appreciated thanks.


05-25-2012, 01:21 AM
Original ignition coils? Replaced the sparkplug caps? They have a 5000 ohm resistor that can become intermittent/fail with heat/time. How's the sparkplug center electrode look? Black is too rich,White too lean, but a light tan is about right.

Checked the valve clearances lately? As valves and valve seats wear, the valve stem moves closer to the cams, requiring thinner shims.

05-25-2012, 01:37 AM
Compression been checked? New/rebuilt engines might have 180-200 PSI, put a few years on it, and maybe now it's 160 or so. An engine will run at 100 PSI, but produce low power. A 10% difference is allowed between cylinders.

05-26-2012, 04:52 PM
Wanna run me through some steps? Sorry never owned a bike like this. So can you please help me? What should I check first, then second, and such. With steps. Thanks.


05-26-2012, 05:19 PM
Let's do some checking; Fuel tank clean,no internal rust? Original ignition coils? Here's how to test the input voltage:

Testing Kawasaki Ignition Coils For Input Voltage

When voltage testing Kawasaki Ignition Coils, the following needs to be done:

1. Remove the fuel/gas tank to access the coils.

2. Fully charge the battery.

3. Using a multimeter, set it up for VDC(Volts, Direct Current), range of 20.

4. Turn on the ignition switch and the run/stop switch to “Run”.

5. Put the multimeter’s RED probe on where the red or red/yellow wire goes on the ignition coil.

6. Put the multimeter’s BLACK probe on either the battery Negative(-) post/terminal or a good frame ground.

7. You should be able to see battery voltage at the ignition coil connection, but this depends on the current draw of other items in the same circuit.

8. If the tested voltage is down to 8-9 volts, you probably need to clean the many and various electrical connectors.

9. To check the spark output at the sparkplugs, use these:
Ignition Spark Testers
Lisle Corporation (http://www.lislecorp.com/divisions/products/?product=312&division=1&category=8)
Lisle Corporation (http://www.lislecorp.com/divisions/products/?product=80&division=1&category=8) Instead of grounding the sparkplug with the sparkplug wire attached, looking for a spark. This method puts the IC Igniter and ignition coils at risk of failure due to high currents, and possible internal shorting.

Cleaning Motorcycle Electrics

1. Get some of the De-Oxit electrical contact cleaner and figure on spending a good day going from the front of the bike to the back. It’s a plastic safe cleaner/preservative. Home of DeoxIT® and HAND-E-GLOVE® - CAIG Laboratories, Inc. (http://www.deoxit.com) is their website. Or use any plastic safe electrical contact cleaner(NOT WD-40 !). Radio shack stores and other electronic supply stores should carry it.

2. On the older Kawasaki's, a majority of electrical connectors are inside the headlight housing requiring removal of the headlight, then the fun begins.

3. Do one set of electrical connectors at a time to avoid mixing up what connects to where. Usually disconnecting, spraying with De-Oxit and reconnecting is about all you'll need.

4. However, when encountering the green crud of corrosion, a brass wire brush may be needed on the pins you can reach.
Some 400-600 grit wet and dry sandpaper strips rolled into a tube should reach the male and female pins in the more difficult to clean connectors.

5. Smoker’s pipe cleaners, cotton swabs and wooden toothpicks work as cleaning aids.

6. Really small electrical connectors may require the use of a welders tip cleaning tool assortment.

7. Most pins in the connectors are coated with a thin plating of tin, and others may be nothing more than copper or brass.

8. If moisture is added, the resulting corrosion lowers the voltage/current being carried causing dim lights, slow engine cranking, slow turn signal responce and lower input voltage to the ignition coils resulting in weak spark.

9. The left and right handlebar switch pods will need attention too as they have circuit functions like turn, horn, run/stop, and start. The older Kawasaki’s have reports of the soldered connections crumbling, if your bike has this problem, just ask, as I’ve got a repair procedure for this.

10. Usually a spritz or two with actuation of the switch is about all needed for these switches unless corrosion is detected and then careful disassembly is required.

11. The ignition switch may or may be not sealed to allow spraying the internal contacts. I urge caution if attempting to open this up as springs, and ball bearings may fly out never to be seen again!

12. If your bike has the older style glass tubed fuses, I suggest replacing them as vibration can cause internal failure. AGX is the type used, and most auto parts stores can get them for you.

13. Clean the fuse holder clips, looking for signs of overheating(discolored insulation, signs of melting).
I use metal polish on a cotton swab, followed by spraying another clean swab with the De-Oxit and then rubbing the inside of the fuse clip.

14. All battery cables must be clean and tight for maximum current transfer. Check the cables going from the Negative(-) battery terminal/post to the engine mounting bolt

15. Also the one going from the Positive(+) terminal to the starter solenoid and from there to the starter motor.

16. If any battery cable feels ”Crunchy” when flexed, replace it as possible corrosion is inside the insulation.

17. Each "Bullet Connector" will have to be sprayed to ensure good connectivity, especially the ones going to the energizing coil of the starter solenoid.

18. The alternator output “Bullet Connectors” are usually behind the engine sprocket cover and will need inspecting and cleaning too.

20. The turn signal light sockets will benefit from a spritz from the contact cleaner along with the tail light/brake light socket.

21. Some brake light switches can be sprayed on the actuating rod, with the spray running down inside to the electrical contacts, others may be sealed requiring replacement if the switch is intermittent in operation.

22. Some people put the Di-Electric Grease on cleaned terminations/connectors, I don’t, as I’ve read/heard it can cause problems when it gets hot, actually insulating the connections, so the choice is yours to use or not.

I think I've covered about all of the electrical systems on the bike.........

“I spent a weekend going through every electrical connection and switch on the bike with a little scotchbrite pad and DeOxit - what a difference! Everything was brighter, gauge backlights, indicator lights, turn signals, I was getting a nicer spark, it fired up quicker, etc. Well worth my time. WELL worth it! “

From a forum member at KZrider.com (http://www.kzrider.com)

Sputtering/surging could be electrical in nature, or fuel delivery/air starvation. The gas cap has a vent built into it, some screws hold the cap together, so remove the screws and inspect the vent for blockage.

Another possibilty is the sparkplug caps, they have a 5000 ohm resistor built into the cap, and the caps unscrew from the sparkplug wires. The caps can be checked with a multimeter set on "Ohms". If confused, just ask and we well help you through this.

05-28-2012, 03:55 PM

Had same issue, spluttered and would not go above 70mph. There is an anti-vacuum valve in the filler cap which was not working. It lets air in as petrol is used. There was a whistling noise after a run which gave it away. I need to replace it but as a temporary fix i have removed it. Not clever as petrol fumes come out but goes a **** sight faster now (track only!!)

05-28-2012, 07:22 PM
Yay someone with a Zephyr. Wanna give me a clue where this vacuum line is and what to do?


05-28-2012, 07:23 PM
As for MFolks. I'm yet to do all of that. I'll let you know. Thanks.


05-28-2012, 08:23 PM
Compression checks are simple to do; Get the screw in tester if possible for better results, if you can't, the type with the rubber piece pressed into the sparkplug hole will do. Remove all 4 sparkplugs, and one at a time, either using the kick starter(if possible) or the electric starter, turn the engine over, writing down the results.

At the conclusion of the test, put about a tablespoon of engine oil in the cylinders and do a retest, again writing down the results. This will tell about the condition of the piston rings and possibly if the valves are out of adjustment. A leak down test would, I believe be better for this.

05-28-2012, 08:50 PM
Mt Gpz 750 did the same thing this spring. Turned out the problem was the battery. Although it showed 12 volts and appeared to be fine, it was dead. Put a new battery in and she runs like new!