The Kawasaki Ninja 650 is one of the most recognizable sportbikes in the world thanks to its iconic green styling.
Ideal for city commuting and technical curve-carving, this versatile mid-sized machine packs a 650cc parallel twin engine.
Like any bike though, it’s prone to issues.
In this article we’ll go over some common issues and how to resolve them.
Table of Contents
1. Kawasaki Ninja 650 Won’t Start
Dead Battery
If your Ninja battery is dead, your bike will click at start up but won’t turn over.
- The battery powers all of your bike’s electrical components, including the ignition, starter, and fuel injection systems.
- In some cases, the battery fails to power the starter because of a low charge. The click sound your bike makes is because the battery has enough juice to zap the starter but not enough to move the coil to start.
- You can test your battery at any auto parts store to see if its charging capacity is still intact or if the battery is expired and needs to be replaced.
- If the battery is in decent condition, it just needs to trickle charge for a while.
- In other cases, if the battery is toast, you’ll need to replace it.
Faulty Starter
If any of the starter’s primary components fail, your Ninja 650 will click at start up but won’t turn over.
- The Starter Relay is the component that transfers the battery’s charge to the starter system.
- The solenoid is the starter’s electromagnet generator that activates your Ninjas starter motor once charged by the relay.
- Once activated, the starter motor sets the motor flywheel into motion, initiating your Ninjas piston process to bring your motorcycle back to life.
If your battery is dead, the starter will click at startup, as the residual charge is enough to juice the relay but not to magnetize the starter motor.
If you’ve tested your Ninja’s battery and are sure it’s got a charge, the next best culprit is your starter motor.
The failures are similar in nature and thus are often confused.
The difference is that the clicking sound in this scenario is the starter gears failing to turn your flywheel over; it’s caused by failed magnetization, either from a lousy magnet or a bad starter motor.
If you have a bad starter relay on the other hand, you won’t hear a clicking sound when your Ninja fails to start up.
This is because the starter magnet can’t get the juice it needs to click if your relay isn’t working properly.
Fuel Pump Issues
In other cases, like the one encountered by the rider quoted below, the problem is either with the fuel filter, pump, or a fuel pressure issue.
“I have a 2011 Ninja […] I keep having problems with the bike sputtering and hesitating once it reaches 6k to 8k RPMs – even sooner when I bust open the throttle to 100% at a lower rpm. I have replaced the pump itself 3 times and the guts inside the fuel pump housing once, and it works fine for the first ride with all three pumps, but when I go to ride again, the same problem has returned, and there is no way I bought three faulty brand new fuel pumps. I’ve cleaned the injectors and fuel rail, and still nothing.“
Overfilled Gas Tank
Overfilling the fuel tank on Ninja 650s with carbon canisters can soak the carbon canisters with fuel, clogging the fuel vent enough to prevent air from entering the fuel tank. If the vacuum is too strong, your Ninja 650 won’t start unless you open the tank.
Here’s an example of one such situation, straight from a Ninja rider:
“My 2013 Ninja 650 sometimes dies and won’t restart. In my case, it’s because I always fill the gas tank to the top before going home and parking my bike). The manual says not to fill the tank past the filler neck, but my fuel gauge won’t read as full if I do that.”
Only certain bikes (California model) have carbon canisters, though.
Other issues could be a kinked fuel line (it sometimes happens if you’re not careful when reinstalling the fuel tank) or a fuel pump going bad.
2. Kawasaki Ninja 650 Won’t Stay Running
Take a crawl through the Ninja 650 forums, and you’ll find more than a few complaints from owners claiming their Kawasaki street bikes start but won’t stay running.
This particular problem seems to be most common among owners of 2007-2010 Ninjas, many of which are available for sale on the used market.
Here’s an example of a rider whose Ninja 650 starts but dies:
“I have a 2006 ninja 650R I bought last year. Ran fine most of the year. Toward the season’s end, it was raining a ton, so the bike sat outside untouched for a month or so. At that time, it wouldn’t run but would fire. When I hit the gas, it just bogs and dies. If I don’t touch the gas, it will run for 15-20 seconds, then die. The oil was emulsified but not frothy, and there is no evidence of coolant in the oil ( it’s not frothy, just milky looking). I’ve flushed & changed the oil, cleaned the air filter, and am going to replace the gas that was left in the tank [but the problem persists].”
More than a few Ninja riders have experienced the same symptoms, which turn out to be caused by water entering the gas tank.
- Inside the gas cap of your Ninja 650 is a rubber hose designed to flush any water out of the cap before it can enter your fuel tank.
- In some situations, the rubber hose is accidentally squeezed closed during servicing.
- Once pinched or bent, the hose prevents the water from properly draining, causing it to accumulate in the cap space.
- Once the water level builds to a certain point, it can flow into your Ninja’s gas tank.
- If a bent gas cap drain hose is why your Kawasaki Ninja 650 won’t stay running, you’ll likely notice water building up around the fuel cap.
While this issue isn’t exactly frequent, when it does happen, it can take a long time for riders to diagnose.
In scenarios like the one that happened to the Kawasaki rider quoted above, it’s a relief to find the problem that caused their Ninja to stop running after starting up is such an easy fix:
“100% on point, my friend [the problem was a pinched gas cap drain hose]. After I pulled the tank, drained it, and put the apple fuel injector cleaner and dry gas, it runs and idles fine now. I did a 2x oil change and ran it for about 30 minutes; there was no smoke from the exhaust, so no head issue; the oil is now 95 % clear.”
Related: How Long Do Kawasaki Ninja 650s Last? (9 Important Facts)
3. Kawasaki Ninja 650 Won’t Crank
If your Kawasaki Ninja 650 doesn’t even try to crank, inspect your battery first, then your starter relay. If these two parts are in working order, ensure your bike is in neutral and that its side stand sensor isn’t broken and free of dirt and grime.
This safety mechanism prevents you from accidentally riding the bike from riding with the stand down.
If the Ninja 650’s side stand switch’s reading capability is impaired by pothole damage or grime, the electrical signal is disconnected. The ECU then believes the kickstand is lowered even if it isn’t, causing the Kawasaki Ninja 650’s engine not to crank.
If the side stand switch is impaired or your Ninja 650 is in gear with the kickstand down, it won’t crank over.
4. Kawasaki Ninja 650 Won’t Start When Hot
If your Ninja 650 runs fine when it’s cold but stalls out when hot, it could be a problem with the bike’s cooling system.
A number of Kawasaki owners have traced their starting issues to engine overheating, often due to a failing radiator fan.
- The Kawasaki Ninja 650 is a liquid-cooled motor, utilizing a radiator, fan, and a coolant system to keep its engine cool.
- Unlike the open-motor design of air-cooled bikes, the liquid-cooled Ninja engine is sealed and pumped with coolant.
- Because of its sealed design, if the cooling system fails for any reason, the engine will overheat rapidly,
In some situations, the Ninja 650’s radiator fan fails way too early, reducing the radiator’s ability to pump coolant significantly. The result is an overheating Ninja engine that won’t start.
Don’t take our word for it; here are a few testimonies from the owner of a Ninja 650 with less than 1,000 miles on the clock:
- “My Kawasaki Ninja is overheating in stop-and-go traffic. I checked the coolant levels, and they are correct. I had the bike serviced at 600 miles, and I am only at 800. I took the bike to the shop, and the fan was not coming on. They ordered a new part and [fixed it] under warranty.”
- “My 2015 Ninja 650 used to overheat. I found out that the 15s specifically had a faulty temp control unit that could burn out. Turns out, I had to get mine replaced, and I had my shop put in a custom switch for the fan. Essentially, hook the fan up to a controller, and then you can turn the fan on and leave it on as you ride, and you don’t have to worry about overheating.“
5. Kawasaki Ninja 650 Won’t Go Into Neutral
Modern Ninjas have a sensor that senses if the bike is Neutral.
The sensor has two functions:
- Alert the display the bike is Neutral to illuminate the N light in the gear display.
- Communicate to the ECU that the gearbox is neutral and not in gear, so the ECU allows the bike to start.
If a Kawasaki Ninja’s neutral sensor is faulty, it will think the bike is in gear even when it’s in neutral.
Not only does this stop the neutral light from illuminating, but it also means the ECU is preventing the Ninja from starting.
6. Kawasaki Ninja 650 Won’t Rev Up
Some Ninja 650 riders claim their bikes turn over but won’t rev up when you crank the throttle. In these cases, the Ninja either has a problematic throttle positioning sensor, or the throttle bodies aren’t balanced correctly.
Here’s an example:
“I have a completely stock 2009 ninja650r w/10,000miles, and all maintenance is entirely up to date and within factory specs following a store-bought genuine Kawasaki repair manual.
I’m having a problem at 4000rpm and below in 4th gear (or third and fifth) while cruising if I turn the throttle a little; either way, I get hesitations. If I let the RPMs drop to 3500 and hold the throttle steady, it gets dead spots almost like it’s going to stall.”
Some riders claim the issue is the factory tuning on pre-2011 models and that it can’t be fixed without installing a Positive Crankcase Ventilation upgrade system to decrease the vacuum in the crankcase, boosting the bike’s RPM and throttle response.
Others claim air intake and exhaust upgrades are enough to boost the lag in revs.
Still, the consensus seems to be issued with failing throttle position sensors and poorly tuned throttle bodies, as not all pre-2011 Ninja riders have problems with static RPMs in the low throttle range. In fact, most of them claim they don’t.
7. Kawasaki Ninja 650 Won’t Go Into Gear
If you crawl through the Ninja forums, you’ll find no shortage of posts like this:
“Sometimes when I pull up to a stop sign or red light, and I pull the clutch in to click it down first to start, and it won’t go, and then it pops into neutral, and I have to kick it to get it to go into 1st repeatedly.”
In some cases, the problem with Ninja 650s not shifting into gear is caused by low oil levels or from running poor quality, burned or contaminated oil through the bike’s engine long after it’s time for an oil change.
In other situations, the shifter linkage is too tight.
And finally, theorists like this Kawasaki rider seem to believe a faulty Positive Neutral Finder causes it:
“I have had this happen, usually when I don’t shift into first before coming to a stop. I let the clutch out a bit, and I can get it in gear. I have read elsewhere of people having the same issue, most likely from the positive neutral finder–you just need to make sure you are in first before coming to a complete stop.”
8. Kawasaki Ninja 650 Not Idling
One of the more common issues we find expressed by first-time riders of the Kawasaki Ninja 650 is issues with low idling.
In some cases, the low idling affects engine performance, while in others, it gives the Ninja 650 problems starting.
The Kawasaki Ninja 650 has a small twist-control knob on the right side of the motorcycle, above the clutch housing. The suggested idle speed varies from year-model but is typically around 1300 RPM.
Riders who are unaware of this adjustment sometimes change the throttle setting accidentally, unaware they can fix it just as quickly.
9. Kawasaki Ninja 650 Keeps Turning Off
Some Kawasaki Ninja 650 owners have reported issues with their bikes stalling out and turning off while riding.
The issue is often accompanied by frequent backfiring.
In a few of the cases we found documented in online reports, the bike’s RPMs would surge, causing the Ninja’s speed to vary independently of the rider’s input.
The issues were reported to have been caused by clogged fuel injectors or dirty air filters in most cases and leaking vacuum systems in a few others.
10. Kawasaki Ninja 650 Battery Keeps Dying
More than a few Kawasaki Ninja 650 owners have reported issues with the battery dying.
In some cases, the battery and lights all die while the rider is riding, while in others, the dead battery is discovered at startup.
Here’s an example of the former scenario as it happened on a 2014 year model Ninja 650:
“So, the bike was acting funny on my way home from work today. The battery light came on for a minute or so, as well as the check engine light. As I stopped, the bike wouldn’t drop idle or decelerate like normal, the display wouldn’t come on and show RPMs, speed, etc., and then it died. So I got off, pushed it over to the sidewalk, hit a pothole with it, and dropped it on the right side. I had the bike towed home, and even with the battery tender on it, I couldn’t get the fuel pump to run or the display to come on during any charging mode, whether it be a 2, 10, or 50-amp charge. No corrosion on the terminals, not a spec of rust anywhere on the bike, garage kept and never ridden in the rain.”
- The battery on the Kawasaki Ninja 650 is tucked away under the bike’s seat. In some cases, the sweltering climate was enough to overheat the battery while it charged.
- In other cases, a faulty Regulator/Regulator overcharges the battery.
- Finally, a few of the rider reports admitted having their Ninja charging at a higher voltage than the battery called for.
All of these scenarios boil off the battery’s electrolytes, causing them to keep dying.
