1975 Kawasaki S3A: Ready to Ride

He was glad he did. “It said something like the bike had low miles and was from an original owner,” Steve recalls. “And then, it said something to the effect that ‘this is a beautiful 3-cylinder bike.’ And I was thinking, wait a minute, is this really a KZ400 twin?” Apparently, a dealership in Pennsylvania had taken the Kawasaki in on trade and posted the ad, and Steve called them up. “I asked if it was a triple, and he said, ‘Oh yeah, it’s a triple.’ Long story short, he texted me photos, and it was definitely an S3 400cc triple.” With that visual confirmation and with the bike still reasonably priced, Steve sealed the deal, hired a shipper, and had the Kawasaki delivered to his home in Waukesha, Wisconsin.

While not the larger 500cc triple like his brother Jeff’s machine, the S3 400 is in some respects a better motorcycle. A January 1974 Cycle World test of the then-new S3 said, “In our mind, the 400 is Kawasaki’s best three-cylinder buy. It handles much better than the 750 — in fact there is no comparison. It’s more economical than the 500 by a wide margin and still has enough performance to get you excited in the mountains.”

The lineage of the Kawasaki S3

Kawasaki’s line of triple-cylinder machines can trace their history back to 1969 and the powerful 500cc H1 Mach III. At that time, the H1 became a best seller thanks to the fact it could hit 60mph in just 4 seconds and offered a blistering top speed of 120mph. Based on that success, Kawasaki followed up with more triple-cylinder machines in 1971 with the 750cc H2, 350cc S2 and 250cc S1.

By 1974, the 350cc S2 became the 400cc S3 when Kawasaki enlarged the engine by taking the bore from 53mm to 57mm. A pressed together crankshaft in horizontally split cases turns on six bearings. Connecting rods mate to the throws via roller bearings, while the piston gudgeon pins are in needle bearings. “Oil for lubricating the engine’s internals is supplied by a plunger-type pump whose delivery rate is controlled by the amount of throttle opening and the engine rpm,” the Cycle World test notes. “This oil under pressure from the pump is delivered through check valves into the cylinder intake ports where it mixes with the incoming fuel/air mixture to lubricate the connecting rods and piston pin bearings.”

Handling intake chores is a bank of three Mikuni VM 26mm carburetors. Given substantial amounts of throttle, Cycle World‘s tester said there was a significant amount of “intake roar,” something they felt could be handled with “better baffling at the air cleaner intake.” Ensuring sparks arrive at the correct moment, the S3 400 Kawasaki uses battery and coil technology with three sets of ignition points. Straight cut gears, meanwhile, transfer power from the crank to the 5-speed transmission. Cycle World‘s tester claimed the gears were closely spaced and allowed “the engine to be kept in its power band while accelerating or blasting down a curvy road.”

Kawasaki debuts rubber mounting

Kawasaki chose to rubber mount the revised 400cc triple-cylinder engine in the double cradle frame in an overall package that weighed 339 pounds dry. Prior to 1974, all Kawasaki triple powerplants were solidly mounted in the chassis, causing significant amounts of vibration. The rubber mounting arrangement in the new S3 virtually quelled the vibes. “At low rpm, as when sitting at a stop light, you can see the engine moving around a little,” the Cycle World story continues, “but practically no vibration is felt through the footpegs at any speed.” When riding down the highway, the tester explained, there was a slight “tingle” in the rubber mounted handlebars. The stock handgrips exacerbated the tingle, they said, and that would have been an easy fix with a pair of aftermarket grips.

The front brake was a single disc while a drum followed at the rear. These were laced into 18-inch rims front and rear and the machine was suspended by a hydraulic front fork and twin rear shocks. A 3.7 gallon gas tank sits atop the well-triangulated frame and 1.6 quarts of injection oil is carried in a tank on the right side of the bike. Produced for just two years, the 1974 S3 and 1975 S3A, 400 triples became the KH400s in 1976 and lasted until 1977 in the United States.

Our feature Kawasaki S3A

Steve knew from looking at the pictures prior to buying his 400cc triple that the 3-into-3 exhaust pipes and mufflers weren’t in great condition, and the paint, in a lime green color, was incorrect. A side panel was missing, and rather uniquely, pinstriped across the top of the tail section was the sentiment “Happy 50th Dad.” As delivered to Steve, though, the 400 appeared to be an honest low-milage machine; one that he could simply clean up and ride. He performed a compression test, went through all of the systems, got the Kawasaki running, and rode it the summer of 2021.

“I got a reproduction side panel and my painter did a 98-percent job matching the green paint,” Steve says. “I had a running bike that looked decent, but at the back of my mind, the pipes didn’t look great and it wasn’t the right color.”

Another thing he learned was the Kawasaki was incorrectly identified on the title by the Pennsylvania DMV as a 1974 S3. His research showed it was in fact a 1975 S3A, and Steve petitioned the Wisconsin DMV to change it. He says, “I had to fight with them about that and they required all sorts of documents and a letter from Kawasaki USA.” He won, however, and the machine is now correctly titled as a 1975 Kawasaki S3A.

Also noteworthy is that the engine and frame numbers match, which isn’t very common on Kawasaki triples. “Rick Brett [Kawasaki triples guru] has a registry of triples from around the world, and he says that’s a one in one thousand chance that the engine and frame numbers will match — and mine do,” Steve explains.

A next level Kawasaki S3A

To take his S3A to the next level, Steve spent the late winter of 2021 and early 2022 sourcing parts. He located two NOS exhaust pipes, and a third one in really good condition that he had re-chromed. Instead of working with the gas tank — which had a scratch and a tiny dent — sidecover and rear tail section of the Kawasaki, Steve removed them, sold them, and acquired a tank and tail section that were in better shape. The side covers are reproduction, and Steve notes, “purists might not agree, but I think the reproductions are probably a little more durable. I’ve had so many old side panels with broken mounting tabs.”

Painting the shiny bits Candy Super Red

Of the paint, Steve says, “I think it had been painted a later model Kawasaki green. It definitely wasn’t the stock color. In 1975, the stock colors were Candy Green and Candy Super Red. I liked the red the best and went with that.” Working with painter Nicholas Brouillard at HeavenlyCustoms in West Allis, Wisconsin, the replacement tank, tail section and aftermarket side covers were sprayed the correct Candy Super Red. Nicholas also laid down a decal set that Steve ordered from Rick Brett.

During this time, Steve stripped the Kawasaki completely down. He needed to repair a bracket on the right side of the frame that carries the mount for the footpeg. “Notoriously, on the 400s, those would bend and mine was bent in at about a 30-degree angle,” Steve says. With the engine out, Steve cleaned and touched up a few areas of the frame with black paint, but for the most part, the chassis still wears its original finish.

While the forks were off, Steve cleaned and serviced the components and rebuilt the sliders with new seals. The front fender was a 9 out of 10, Steve says, but it had some road rash at the front corner. He found a NOS replacement, and it was in near perfect condition. At the back of the machine, new shocks were added. The engine was never taken apart, as the compression was within spec and it had not been losing or burning any crankcase oil.

“The other thing about this bike is I wanted to ride it,” Steve says of his resurrection effort. “I wasn’t after a concours restoration, I just wanted to make it look as stock as possible and make it so it could be ridden reliably.” To that end, Steve updated all of the electronics, replacing the regulator and rectifier. He dispensed with the mechanical points and installed an Accent solid state electronic ignition system. Also replaced were the coils, plugs, high tension leads and caps. On the intake side of the equation, the carburetors were stripped, cleaned and fully serviced.

As far as Steve can tell, the seat is original Kawasaki vinyl and foam on the pan. When he bought it, the S3A showed just over 4,000 miles on the odometer and he believes that it is likely genuine. After his restoration, the Kawasaki now shows more than 4,800 miles.

It’s a fairly simple machine to bring to life. “Just flick the gas on, click half choke, and one or two kicks and it fires right up,” Steve says of the kickstart-only Kawasaki. “It’s got a thumb choke lever, and I’ll usually hold it at half for 20 seconds, let the choke out and let it warm up a minute longer and then go. With all of the new electronics it fires up and runs really well.”

He continues, “The ride is great, and it’s really quick. It’s super smooth, goes through all the gears well and it handles nicely and pulls well. It likes to rev, and it really wakes up at mid to upper throttle, pulling strongly from 5,000rpm to 9,000rpm.”

Taking Steve’s triple-cylinder Kawasaki story full circle, his brother Jeff still owns the H1 500, and Steve got to ride the bike he rode to high school again last summer. “It’s still a little bit scarier to ride, mostly in terms of handling. The 400 seems more refined and it’s a very nice triple to own. I’ll get out for short rides during the week, or slightly longer rides on the weekend,” he says, and concludes, “It’s great fun, and makes me feel like I’m back riding to high school again, just without any lectures or exams.” MC

Originally published as “Ready to Ride” in the September/October 2023 issue of Motorcycle Classics magazine.