Finding a clean Kawasaki 650 SX these days feels like uncovering a time capsule from the late 80s when stand-up jet skis were basically the kings of the lake. It wasn't just another personal watercraft; for a lot of us, it was the gateway drug into a lifelong obsession with two-stroke smoke and the kind of leg workout you can't get at a gym. While the world has mostly moved on to massive three-seater couches that can go 70 mph, there's something about the 650 SX that keeps enthusiasts scouring Marketplace and Craigslist every single weekend.
Why the 650 SX Still Holds Up
The Kawasaki 650 SX hit the scene as a bigger, beefier brother to the legendary JS550. Back then, if you wanted to go fast and stay stable, you looked at the 650. It featured a 635cc twin-cylinder engine that was, and still is, considered one of the most bulletproof powerplants Kawasaki ever produced. If you've ever spent time working on old skis, you know that these engines just want to run. Even after sitting in a garage for five years under a pile of old moving boxes, a little fresh fuel and a jump start are usually all it takes to hear that familiar brap again.
What makes this ski so special isn't just the engine, though. It's the hull design. It's wider and more stable than the 550, which made it the perfect "transition" ski. Beginners could actually stand up on it without falling over every three seconds, but it still had enough agility to keep an experienced rider entertained. It carves differently than a modern Yamaha SuperJet—it's a bit more "locked in" due to the hull shape, but once you learn how to weight the tray, you can make it do some pretty impressive things.
The Learning Curve and Handling
If you're coming from a modern 4-stroke sit-down ski, jumping on a Kawasaki 650 SX is going to be a humbling experience. It's not going to do the work for you. You have to be active. You're using your core, your quads, and your grip strength just to keep the nose from diving or the rear end from sliding out in a way you didn't intend.
The 650 hull is known for being a bit "sub-prone" if you don't know what you're doing. Because of the way the weight is distributed, if you chop the throttle while the nose is pointed down, you're going for a swim. But that's the fun of it! The physical connection between the rider and the machine is so much more intense than it is on a modern boat. You feel every ripple in the water, and every successful carve feels like a genuine achievement.
The Bulletproof 635cc Engine
Let's talk about that motor for a second. The 635cc engine in the Kawasaki 650 SX is a masterpiece of simplicity. It's a piston-port design, which means there are fewer moving parts to worry about compared to reed-valve engines. For the weekend mechanic, this is a dream. You can basically rebuild the entire top end on a workbench in an afternoon with basic hand tools.
The stock power is decent—somewhere in the neighborhood of 50 to 52 horsepower—but the real magic happens when you start messing with the exhaust. The factory "pipe" is pretty restrictive. If you can find an old Westcoast or Coffman's pipe for one of these, it completely changes the personality of the ski. It wakes up the bottom end and gives it that "snap" that makes jumping wakes so much more fun.
One thing to keep an eye on, though, is the oil injection. Most owners of the Kawasaki 650 SX ended up deleting the oil injection pump and switching to premix. Those old pumps were reliable for a decade or two, but if one fails today, you've got a seized engine before you even realize something is wrong. Mixing your gas at 40:1 or 50:1 is a small price to pay for the peace of mind that your engine is actually getting lubricated.
Modding the Legend
If you buy a Kawasaki 650 SX today, it's almost guaranteed that someone has already tinkered with it. Maybe it has an aftermarket intake grate, a ride plate, or an upgraded impeller. These are the "big three" mods that every owner should consider.
- The Intake Grate: The stock grate is okay, but a "scoop" style grate will help the ski stay hooked up in choppy water.
- The Ride Plate: An extended ride plate helps keep the nose down and reduces "porpoising," which is that annoying bouncing motion these skis do when you're pinned at full throttle.
- The Impeller: Switching from the old stainless or aluminum stock prop to a modern progressive pitch impeller will give you better acceleration and a bit more top-end speed.
Beyond the performance stuff, a lot of guys spend their time on cosmetics. The late 80s and early 90s graphics were let's say "vibrant." Some people love the neon pink and teal aesthetic, while others prefer to strip it down and go with a clean, modern turf job. Speaking of turf, if the ski you're looking at still has the original rubber floor mats, that's the first thing you should replace. A sheet of Hydro-Turf makes a world of difference in how much control you have over the ski.
What to Look for When Buying
Thinking about picking up a Kawasaki 650 SX? You're going to see them ranging from $500 basket cases to $3,000 mint-condition survivors. Here's the reality: don't buy one without a compression test. It takes two minutes and will save you hundreds of dollars. You're looking for somewhere around 130-150 PSI in both cylinders, and ideally, they should be within 5-10% of each other.
Check the hull for "spider cracks" in the gelcoat. A few are normal for a 30-year-old ski, but deep cracks near the motor mounts or the pump area could mean it's been jumped hard and landed flat too many times. Also, look at the electronics. The "green box" (the CDI) can be finicky, and finding OEM replacements is getting harder every year, though the aftermarket has stepped up to fill the gap.
Lastly, check the gas tank. Old fuel lines tend to degrade and turn into a gummy mess that clogs up the carburetors. If the fuel lines look original (usually a brownish-clear color), plan on replacing them immediately with some high-quality Tygon tubing.
The Community and Longevity
One of the coolest things about owning a Kawasaki 650 SX is the community. There are forums and Facebook groups dedicated entirely to these old "vintage" skis. If you run into a tuning issue or can't figure out why your starter is clicking, there are thousands of people who have dealt with the exact same problem and are happy to help.
Parts availability is surprisingly good, too. While Kawasaki might not stock every single bolt anymore, companies like SBT and various boutique shops keep these things on the water. You can still get gaskets, pistons, seals, and bearings without any trouble. It's one of the few hobbies where you can own a "classic" and not have to spend your life's savings just to keep it running.
Final Thoughts
The Kawasaki 650 SX isn't just a jet ski; it's a piece of history that you can actually use. It's small enough to fit in the back of a pickup truck, simple enough to fix in your driveway, and fun enough to make you feel like a kid again. Sure, it might be louder and smell more like gasoline than a brand-new Sea-Doo, but that's part of the charm.
When you're out on the water, leaned over in a sharp turn with the engine screaming and the spray hitting your face, you realize why people still love these things. It's raw, it's visceral, and it's pure fun. Whether you're a collector or just someone looking for a cheap way to get on the water, the 650 SX is a legend for a reason. It's got soul, and in a world of computerized, plastic-heavy watercraft, that's becoming a very rare thing indeed.