How To Replace The Battery On A Kawasaki Ninja 300

(and the Brake-Hose Trick That Makes It Easy)

The day I shot this, I had about 12 motorcycles packed in YouMotorcycle’s shop and not a lot of move to room around, so I wanted to get this Ninja 300 battery replacement done good and fast. This is one of the easiest battery job around, but with these simple steps, you’ll be able to replace your battery yourself with no issues.

If your Ninja 300 is cranking slow, dying overnight, or just due for a fresh battery, you can do this yourself in about 10 minutes with basic tools. No dealer, no motorcycle towing company, no drama.

I’ll also show you two things most people skip — a dirt-cheap trick that stops those little terminal nuts from vanishing into the bike, and how to add a battery tender pigtail so you never get stranded with a dead battery again.

Tools and parts you’ll need

Nothing exotic. You’ll want:

• 4mm and a 5mm Allen keys
• A Philips screw driver or a 10mm socket bit and socket wrench for the terminal nuts
• A YTX9 battery – I always recommend going with a quality brand like Yuasa, rather than the cheapest no-name you can find, but in this case I used my favorite cheap battery brand: Mighty Max (not sponsored, just saying).

Optional but worth it:

• A battery tender pigtail compatible with your brand of motorcycle battery tender
• A short length of fuel hose and scissors (I’ll explain later)

Step 1: Getting to the battery

Start by popping the seat rear off by using the key switch under the seat above the rear tire.

From there you’ll need to remove a 4mm Allen bolt on each side cover, and then just pull them out to remove them.

Now you’ll have exposed the 5mm Allen bolt on each side that holds the seat in place. Remove those, and when you do, watch for the little metal bits that like to fall out and disappear. Set them somewhere safe; you’ll need them on reassembly.

There’s a cover above where your battery sits. There’s one more screw to remove it, and then just slide it to the bike’s right, and out of the way, and there’s your battery sitting right there.

Step 2: Pull the old battery, negative first

This is the part people get wrong, so do it in order: disconnect the negative terminal first, then the positive. Doing negative first is the safe way to avoid shorting anything against the frame.

One heads-up from my install:

One of the terminal nuts dropped down into the bike while I was working. It happens. You can fish it out later, but it’s exactly the kind of annoyance the next trick fixes. Once both terminals are off, pull the battery aside, reach in, and lift it out.

Step 3: The fuel-hose trick that makes this easy

Here’s the part nobody shows you, and it’s almost free. Grab a short piece of fuel hose and cut a couple of small sections with scissors, about the size of the battery terminal nut.

Before you drop the new YTX-9 battery in, slip a little piece of that hose under each terminal nut. Put the nut and the hose piece in to the battery terminal at the same time. The hose fills the space and holds the nut in place so it doesn’t fall out while you’re lining everything up. The hose also means the nut stays in place when you’re screwing the bolt in, so it stays perfectly lined up and easy and quick to do.

Without the hose in there, this can be a finicky and annoying task. That one tweak turns the fiddliest part of the job into something you can do one-handed. When the hose is doing its thing, this job is so much easier than fighting a loose nut that’ll want to move inconveniently or fall down into the fairing.

Line the new battery up the same way the old one came out: negative on its original side, positive on its original side, and drop it in.

Step 4 (optional): Add a battery tender pigtail

Here’s another thing that will make your life easier in the future that a lot of people won’t do: install a battery tender pigtail.

A battery tender pigtail stays bolted to the battery permanently. It’s like an extension cord for your battery, allowing you to plug in your battery to be charged, without having to take everything apart to access your battery. When your Kawasaki Ninja 300 is going to be sitting for a week or more, you just plug your charger straight into that pigtail. No more dead batteries, no more having to take your motorcycle half apart to get to your battery. If you do this you’re setting yourself up for success for the future.

To install it, go positive first: run your nut through the positive terminal, through the pigtail, and onto the battery. It can be a little tricky to line up without the hose, so wiggle it until it seats. With the hose under the battery terminal nut it will be easy. Do the negative side the same way. Route the loose connector out where you can reach it. Check out the video to see where and how I ran mine.

Step 5: Learn from my mistake and tighten everything

Make sure both terminals are good and tight before you button everything up.

I’m not being fussy here. I once had a bike die on me on the highway because a terminal worked itself loose. Loose terminals are exactly how a running bike suddenly isn’t running anymore. Snug them down properly. You might want to use a 10mm socket bit and a socket wrench to really get them tight – just don’t damage the battery by overtightening!

Step 6: Test, then reassemble

Before you put it all back together, hit the starter and make sure everything’s alive. Mine fired up right away and purred like a kitten. It’s first time starting in over a year!

Now reassemble in reverse:

• Pop the battery cover’s tab back in its hole and screw it down
• Refit the seat using the 5mm (doing it on the floor will make it easier to see how to line the bolts up, make sure not to lose the little metal bits)
• Reinstall the side covers by lining up and popping in their four pins pins and then tighten up with the 4mm bolt to finish
• Put the rear seat back on

Bottom line

The Kawasaki Ninja 300 battery replacement isn’t the the most beginner-friendly battery swap in the world, but if you follow these instructions you’ll realize it’s still just a handful of Allen bolts, a YTX9, and ten minutes of your time.

The fuel-hose trick saves you the most aggravating part, and adding a battery tender pigtail means you probably won’t be doing any battery swaps for many many years.

Do it once, do it right, and tighten those terminals!

Adrian