Editorial Word: This text initially appeared within the August 2023 situation of Roadracing World & Motorbike Expertise journal. Scroll all the best way down to observe the video from the intro occasion at Thunderhill Raceway Park.
Intro: Kawasaki Ninja ZX-4RR
Screaming Enjoyable!
By Chris Ulrich
ZX-4RR world mannequin paid off, with gross sales exceeding expectations. They’ll convey in additional for 2024. The theme is more-usable energy. Picture by Kevin Wing.
I used to be tucked in and flat-out with the throttle pinned because the revs climbed towards 15,000 rpm. I shifted into fourth gear earlier than lifting my head and sticking my knee out simply sufficient to create some drag as I changed into Thunderhill’s quick Flip 9 kink with out respiratory the throttle. It had taken me a few periods and some setting adjustments to get the place I might undergo the flip wide-open, however as soon as I dialed within the bike’s set-up and my line, I might run by way of it at 107 mph lap after lap.
Ripping by way of corners flat out and selecting up the throttle far sooner than wise introduced again recollections of ripping round on my two-stroke Honda RS125 as an adolescent. Besides I used to be on a 400-class inline four-cylinder with a steel-tube chassis and avenue tires. The gear was wildly totally different, however the method used to hustle them across the racetrack is fairly near being the identical. And, generally, considering (or over-thinking) about that progress, it’s mind-blowing how far mass-produced sportbikes have progressed through the years.
Why This Bike?
Lately, excessive efficiency, small-displacement, four-cylinder sportbikes should not seen within the American market. Many of the bikes offered within the U.S. on this displacement class are price-point machines, so that they price much less to construct and purchase, and have lower-performance engines, chassis, and various parts. Within the case of Kawasaki, its present entry-level mannequin is the Ninja 400, powered by a Parallel Twin engine making lower than 35 horsepower inventory, and coming with typical forks and a spindly, steel-tube chassis. Different merchandise within the 400cc class—the twin-cylinder Yamaha YZF-R3 and the single-cylinder KTM RC390—share the identical built-to-a-budget traits. A step up by way of efficiency leads the buyer to the Yamaha YZF-R7, Kawasaki Ninja 650, and Suzuki SV650, however all of them have an analogous cost-down manufacturing directive and simple using traits. None of them are pure-bred performance-oriented sportbikes.
Kawasaki is now altering the entry-level sportbike sport with the brand new Ninja ZX-4RR, a 399cc Inline four-cylinder with a high-performance chassis, ride-by-wire throttle, and a premium electronics bundle, priced at $9,699. It’s a daring technique, however brings one other bike to the market with attainable efficiency for a daily rider and sufficient efficiency to entertain an skilled track-day or racing fanatic. Kawasaki hopes that 15% of riders who buy the ZX-4RR take it to the racetrack for observe days or racing. If that occurs, it will imply that house owners are 40% extra prone to take their bike to a racetrack than the following bike in Kawasaki’s sportbike line up, which is the 636cc ZX-6R.
Ninja ZX-4RR TECH
Evaluating the brand new Kawasaki Ninja ZX-4RR to the opposite bikes in its displacement class doesn’t do it justice, as a result of Kawasaki’s 40%-sized Superbike is a ripper! The Ninja ZX-4RR is actually in a efficiency class of its personal. Many of the tech was beforehand lined within the March situation, however let’s hit a couple of of the excessive factors.
The ZX-4RR has the identical feel and appear as its bigger displacement brothers. It has a low gas tank and smooth bodywork with styling much like the ZX-6R. A big ram-air scoop within the heart of the higher fairing takes benefit of the high-pressure zone to ship chilly air to the airbox through a tube that snakes across the left fork leg. The aerodynamic tailsection is smooth.
The Ninja is powered by a liquid-cooled, 16-valve, double-overhead cam (DOHC) 399cc Inline-4 engine with a 57mm bore and a 39.1 mm stroke. Like different high-performance Kawasaki fashions, the ZX-4RR has machined combustion chambers and pistons which might be forged to match. A friction-reducing molybdenum coating has been utilized to the piston skirts to cut back friction. The valve pockets on prime of every piston are extensive to accommodate the 2 giant (for its displacement) 22.1mm consumption and two 19mm exhaust valves which might be actuated by a set of cast hole core camshafts. The valve angle is slim, with the intakes set at 11.8 levels from the cylinder centerline and exhausts at 13 levels, so included valve angle is 24.8 levels. The air -fuel combination is fed to the ZX-4RR engine through a set of electronically-controlled 34mm throttle our bodies. To enhance consumption effectivity, Kawasaki engineers labored to straighten the consumption path from the throttle our bodies to the valves. The compression ratio is a relatively-low 12.6:1, which permits the little Superbike to run on 87-octane gas.
The engineers paid shut consideration to lowering engine mechanical losses and vibration. A light-weight flywheel decreases rotating mass. The crankshaft has been balanced to cut back vibration and the light-weight rods had been put by way of a carburizing remedy to harden the metal and enhance sturdiness. An fascinating add to the ZX-4RR is a deep sump oil pan, to keep up oil stress throughout acceleration and deceleration.
The chrome steel 4-2-1 exhaust system has 31.8mm head pipes, and all 4 are related with cross tubes to stability out the exhaust pace and the amount flowing although every pipe. Kawasaki additionally positioned the three catalyzers (required to fulfill strict emission requirements) within the collector, so riders can simply add a slip-on muffler and nonetheless be compliant.
The Kawasaki Ninja ZX-4R has an electronics suite with options normally reserved for a 1000c flagship mannequin. Headlining the digital capabilities is the Kawasaki Traction Management (KTRC) system, which options three ranges of traction management (TC), plus an off place. As ordinary, TC Mode 1 is the least intrusive, Mode 2 is within the center, and Mode 3 delivers essentially the most intervention. The ZX-4RR doesn’t have an IMU, so interventions are primarily based on wheel speeds and the speed of rpm change. Two Energy Modes can be found; Low reduces energy and the throttle opening price, whereas Full has a extra aggressive throttle map. (After using the bike for a day, I consider the Full energy throttle map provides extra throttle opening than the rider is definitely asking for in some rpm ranges.) 4 Using Modes—Sport, Street, Rain, and Rider—can be found, with Sport, Street, and Rain pre-loaded with applicable settings for every. Deciding on Rider Mode permits customizing the ability supply, by mixing the KTRC settings and Energy Mode settings individually. One other premium function is the addition of a Kawasaki Quickshifter system, which permits clutchless upshifts and downshifts.
Bluetooth functionality has been added to the ZX-4RR to permit connection to Kawasaki’s Rideology app. The app permits the consumer to log rides, make Mode adjustments, obtain messages on the sprint, and obtain necessary car information. Clearly, the telephone should be in vary to run the real-time options like GPS.
Transferring onto the chassis, Kawasaki engineers selected to make use of a steel-tube trellis primary body that connects to giant swingarm pivot plates. Tubular metal can also be used for the subframe, which isn’t detachable from the principle body.
Kawasaki says the engineers used the ZX-10R as a reference when deciding on the relative engine place, pivot place, heart of gravity, and castor angle. There’s not a direct correlation contemplating that the ZX-4RR has 23.5 levels of rake and 96.5mm of path whereas the ZX-10RR comes with 25 levels of rake and 106.6mm of path. To be honest, the smaller and lighter bike doesn’t want as a lot rake and path, but it surely additionally explains why elevating the entrance improved the entrance really feel of the ZX-4RR (extra on that later).
The ZX-4RR comes with Showa suspension fitted on each ends. On the entrance there are 37mm Showa Separate Operate Fork-Huge Piston (SFF-BP) inverted forks. The SFF-BP system separates the spring and damping features of the fork legs. Within the case of the ZX-4RR, the correct fork leg has spring-preload adjustment solely, whereas the left fork takes care of the damping duties. There isn’t a damping adjustment on the entrance, however the ZX-4RR nonetheless performs effectively on observe. The SFF-BF forks assist scale back unit prices with out sacrificing a ton of efficiency. A Showa Stability Free Rear Cushion Lite (BFRC-Lite) is used on the rear of the ZX-4RR. In contrast to the forks, the BFRC has adjustable compression and rebound damping, plus spring pre-load adjustment. The shock mounts on to a comparatively lengthy metal swingarm.
Stopping the ZX-4RR is a set of Kawasaki-labeled four-piston Nissin brake calipers that place a bigger 32mm piston above a 30mm piston in all sides. The calipers clamp onto a set of fully-floating 11.4-inch (290mm) rotors. To adjust to Euro5 security requirements, the Kawasaki has a Nissin ABS unit that reads wheel speeds to find out slip situations.
Spinning Laps On Monitor
I might inform the Ninja ZX-4RR was not a traditional small-displacement, cost-down mannequin a couple of corners into my first lap round Thunderhill Raceway Park. I match on the bike fairly effectively; the rider triangle is sporty however not too cramped. The seat is agency and the gas tank gives loads of assist.
I used to be snug instantly on the ZX-4RR and that meant I rapidly discovered the restrict of the inventory suspension settings. I used to be instantly into the bump cease on the entrance, and the rear setting didn’t permit me to complete the corners the best way (and on the pace) I wished to. Whereas the inventory suspension settings had been too comfortable for me through the first session, I might nonetheless inform the ZX-4RR has a very good engineering basis. That means, the forks and head tube didn’t flex beneath heavy braking and turn-in; the bike didn’t wallow although the corners; and the rear didn’t twist and bind up on nook exits.
With the Digital Throttle Valve (ETV) system Energy Stage set to Full and the Kawasaki Traction Management (KTRC) set on Stage 1, the bike made good energy, however was slightly lazy throughout acceleration. Turning the KTRC off later within the day woke the ZX-4RR up. The quarter-size Superbike was happiest working in a 4,500 rpm vary from 10,000 to 14,500 rpm; the ability nosed over because it approached the 15,000-rpm rev restrict. (Early promotional supplies mentioned the ZX-4RR turned to 16,500 rpm, however that was earlier than the EPA’s sound police stepped in.) Prime pace is spectacular for a 400; at Thunderhill, I used to be capable of tag the rev limiter in fourth gear with a terminal pace of 121 mph simply earlier than letting off and dragging the entrance brake to set the entrance forks earlier than peeling into Flip 1.
Transferring to nook entry, the braking energy and really feel from the Nissin four-piston calipers and twin entrance brake discs had been each nice. However the conduct of the twist grip throughout deceleration was unusual. I might really feel the twist grip transferring, mimicking the throttle plates, at sure factors within the deceleration zone. This didn’t upset the chassis or add inputs and I ultimately discovered to disregard the motion, but it surely was alarming through the opening laps! The Kawasaki Quickshifter was good throughout acceleration, and every upshift was clean and exact. However the ZX-4RR had an inclination to catch a false impartial downshifting between the 4th and Third-gear, so I needed to be actually deliberate on that downshift if I used to be utilizing auto-blip—and I lastly began utilizing the clutch after my fifth missed shift. The throw is a bit lengthy between these gears, so it takes care to get the shift. (The downshift between fourth and third can also be slightly dodgy on older Honda CBR1000RR and BMW S100RR fashions fitted with auto-blip, so it generally occurs.)
With the primary session over, I went to work on the chassis, making the most of the restricted, but efficient, suspension changes obtainable from the 37mm SFF-BP inverted forks and BFRC-Lite shock. My first change was including 1.5mm of spring pre-load to the forks and shock. This alteration raised the bike, which improved cornering clearance and added assist on each ends. As anticipated, I used to be then capable of brake later at nook entry; entrance stability on the apex improved barely; and the assist on the rear helped the bike end the corners. I then added a ¼-turn of compression and rebound damping to the Showa BFRC rear shock to enhance assist and decelerate the pitch. This actually helped me rotate the bike by way of the center a part of the nook. And growing the rebound slowed the speed at which the shock returned, so braking stability was improved and the ZX-4RR was calmer on nook entry.
An even bigger, extra time-consuming change was including 2mm of trip peak to the entrance of the ZX-4RR by transferring the tubes down within the triple clamps. Including trip peak to the entrance modified the burden bias, which made the Ninja extra calm general. The bike was then extra secure on nook entry and on the apex, however the entrance sat slightly excessive to actually end the nook. So, I then eliminated 1mm of preload from the entrance to stability out the adjustments, turned off the traction management, and rode the bike for the remainder of the day with these settings.
As soon as the settings had been within the zone, the Ninja ZX-4RR was actually loads of enjoyable to trip. The chassis was secure within the low and mid-speed corners in addition to within the quick sweepers at Thunderhill, and the comparatively low general weight and lack of crankshaft inertia made it simple to show in, and nimble after I flicked side-to-side. It rotated and completed the corners effectively.
Rear grip wasn’t a difficulty; it shouldn’t be with round 65 horsepower on the rear wheel. I did should always work on getting the throttle open as early as doable through the day. Convincing myself to seize a handful of throttle with loads of lean angle is at all times an adjustment when coming off larger-displacement bikes!
General really feel from the metal chassis was good. I had an enormous front-wheel slide going into Flip 5 late within the day, however I felt it begin to go early and was capable of barely lower brake stress and dig my knee in to save lots of myself from hitting the bottom. On the rear, the texture from the chassis helped me acquire the boldness to aggressively open the throttle mid-corner. General, Kawasaki acquired the rigidity stability of the chassis proper, a minimum of on the Dunlop Sportmax GPR-300 radial tires.
Engine efficiency improved with the ZX-4RR set to Full energy with the KTRC turned off. Throttle response was extra direct and the engine gained rpm extra rapidly throughout acceleration, and recovered rpm quick between shifts. Prime pace was additionally improved and I noticed 120 mph on the sprint. I get it, digital aids are a promoting level, and the European requirements require them within the identify of security. However for my part, a very good rider doesn’t want traction management on a motorbike with lower than 150-horsepower.
By the tip of day, I’d accomplished over seven 30-minute periods on the racetrack and it felt like I might preserve using for seven extra periods. I rode the Ninja ZX-4RR to the restrict of the tires, chassis, and my means all day. But I wasn’t fatigued mentally or bodily, and I had a blast. That’s the greatest a part of smaller-displacement high-performance bikes: Getting right into a rhythm, pounding out the laps, and having a lot enjoyable. The Kawasaki Ninja ZX-4RR has the chassis and engine efficiency to entertain a seasoned Superbike man like me, however is mellow sufficient that anybody can trip it. Which makes it stand alone in its spot within the trade.
Specs: 2023 Kawasaki Ninja ZX-4RR
Engine Configuration: Inline 4, 4-stroke,
Engine Displacement: 399cc
Engine Cooling: Liquid
Compression Ratio: 12.3:1
Combustion Chamber Design: Pentroof
Valves Per Cylinder: 4
Consumption Valves Per Cylinder (Materials): 2 (Stainless Metal)
Exhaust Valves Per Cylinder (Materials): 2 (Stainless Metal)
Bore x Stroke: 57.0 mm x 39.1 mm
Connecting Rod Size (center-to-center): N.A.
Connecting Rod Materials: Metal
Claimed Peak Horsepower: N.A.
Claimed Peak Torque: 26.5 lbs.-ft. @ 11,000 rpm
Engine Redline: 15,000 rpm
Valve Angle (Included): 11.8 levels Consumption/ 13 levels Exhaust
(24.8 levels)
Combustion Chamber Quantity: N.A.
Valvetrain Kind: DOHC, Curler Chain Drive, Bucket
Tappets, Shim-under-bucket Lash Adjustment
Valve Adjustment Interval: 15,000 miles
Consumption Valve Diameter: 22mm
Exhaust Valve Diameter: 19mm
Consumption Valve Stem Diameter: N.A.
Exhaust Valve Stem Diameter: N.A.
Consumption Valve Most Elevate: N.A.
Exhaust Valve Most Elevate: N.A.
Consumption Valve Timing:
Open BTDC: 23 levels
Closed ABDC: 63 levels Period: 266 levels
Exhaust Valve Timing:
Open BBDC: 55 levels
Closed ATDC: 25 levels
Period: 260 levels
Valve Timing Measurement Level (carry): 0.3mm
Gasoline Supply System: Keihin Digital Gasoline Injection
Throttle Physique Venturi Measurement: 34mm
Air Filter Kind: Pleated Paper
Exhaust System Kind (Materials): 4-2-1 (Stainless Metal)
Ignition System: Digital
Rider Aids:
IMU: No Traction Management: 3 Ranges, Plus Off
Slide Management: No
Wheelie Management: No
ABS: Sure (Nissin ABS Unit)
Quickshifter: Kawasaki Fast Shifter Up/Down (KQS)
Journey Modes Accessible: Rain, Street, Sport, Rider
Lubrication System: Moist Sump
Oil Capability: 3.8 quarts (3.6 liters)
Gasoline Capability: 4.0 gallons (15.1 liters)
Transmission Kind: Cassette, 6-speed, Fixed Mesh
Clutch Kind: Multi-plate, Moist, Again-torque limiting,
With Acceleration Help
Clutch Actuation System: Cable
Clutch Spring Kind: Coil
Variety of Clutch Springs: 3
Variety of Clutch Plates: 14
Drive Plates: 8
Pushed Plates: 6
Major Drive: Gear (Straight-cut)
Major Drive Gear Tooth (Ratio): 14/41 (2.029:1)
Last Drive Sprocket Tooth (Ratio): 14/48 (3.429:1)
Transmission Gear Tooth (Ratios):
sixth: 28/27 (1.037:1)
fifth: 30/26 (1.154:1)
4th: 32/24 (1.333:1)
Third: 34/21 (1.619:1)
2nd: 37/18 (2.056:1)
1st 41/14 (2.929:1)
Transmission General Ratios:
sixth: 7.21:1
fifth: 8.03:1
4th: 9.27:1
Third: 11.29:1
2nd: 14.30:1
1st: 20.38:1
Theoretical Pace In Gears At Redline:
sixth: 153 mph
fifth: 136 mph
4th: 118 mph
Third: 97 mph
2nd: 77 mph
1st: 53 mph
Engine Pace At 60 mph: 5,880 rpm
Body Design (Materials): Trellis (Metal)
Rake/Path: 23.5 levels/ 3.8 inches (96.5mm)
Claimed Wheelbase: 54.33 inches (1,380mm)
Claimed Swingarm Size: 22.5 inches (573mm)
Seat Peak: 31.5 inches (800mm)
Footpeg Peak: 12.4 inches (315mm)
Handlebar Peak: 33.7 inches (857mm)
Steering Stem to Seat Heart: 26.4 inches (670mm)
Entrance Forks: Showa Inverted SFF-BP, Cartridge
Fork Tube Diameter: 37mm
Fork Changes:
Rebound Damping: None
Compression Damping: None
Spring Preload: 10-turn Vary
Entrance Wheel Journey: 4.7 inches (120mm)
Rear Wheel Journey: 5.3 inches (134mm)
Rear Suspension Kind: Showa BFRC-Lite Single Shock
Rear Shock Changes:
Rebound Damping: 3-turn Vary
Compression Damping: 5-turn Vary
Spring Preload: 10mm Vary
Entrance Brakes: 290mm (12.2-inch) Twin Discs, 4-piston
Radial-Mount Nissin Monoblock Calipers
Rear Brake: 220mm (8.7-inch) Disc, Single-piston Nissin Caliper
Entrance Wheel: 3.50 x 17.0-inch Solid Aluminum Alloy
Rear Wheel: 5.50 x 17.0-inch Solid Aluminum Alloy
Entrance Tire: 120/70-ZR17 Dunlop Sportmax GPR-300 Radial
Rear Tire: 160/60-ZR17 Dunlop Sportmax GPR-300 Radial
Claimed Moist Weight: 415 kilos (188.2 kg)
Claimed Weight Distribution, Proportion: N.A.
GVWR 811 kilos (1,788 kg)
General Size: 78.3 inches (1,990mm)
General Width: 20.1 inches (765mm)
General Peak: 43.7 inches (1,110mm)
Floor Clearance: 5.3 inches (135mm)
Prompt Retail Worth: $9,699
