Super Sporting the Kawasaki ZX-14 with Head

By Quantum Motorsports

While the title of this article carries a bit of humor and innuendo, our intent is to provide you with both an interesting and informative read and technical insight into what is required to extend the performance limits of Kawasaki ZX-14. At Quantum, we devote a great deal of time to understanding the design and engineering of engines before we attempt to modify them through machining and/or installing aftermarket components. By taking this approach, our efforts mirror what the factory would do to extend and improve upon performance. We always attempt to maintain the integrity of the original design.

When Kawasaki introduced the ZX-14 in 2006, it was done to avenge the defeat they had been handed by the Suzuki Hayabusa. Since its introduction in 1999, the Hayabusa rapidly became the top selling large displacement import super bike because of its displacement, engine design and its performance in both drag and land speed racing. Much of its appeal lies in quick throttle response and a broad power band. 

With this in mind, Kawasaki very much had Suzuki in its cross hairs when designing the ZX-14 and modified the ZX-12 platform with the goal of outperforming, if not crushing, its erstwhile nemesis. Realizing its 1200 cc engine had to be radically changed to compete with the broader power band of the Hayabusa, Kawasaki simultaneously resized and reengineered the older design to achieve its new goals of higher peak power supported by a broader torque curve. Power through RPM’s had to be rethought.

To accomplish this goal Kawasaki recognized its new engine would need to have higher piston speeds as piston speeds drive volumetric efficiency which, in turn, drives torque.

The new 1362 cc power plant has a bore of 84 mm and a stroke of 61 mm; its predecessor had a bore of 83 mm and a stroke of 55.4 mm. Most of the increase in displacement has come by way of stroke and the engine is less over-square with a bore to stroke of 1.38. In comparison, the Hayabusa has a bore to stroke of 1.28 and the ZX12 has a bore to stroke of 1.50. As Kawasaki planned and as one would expect, power comes on faster than previously and advertised peak power is now at 9,500 RPM……fully 1,000 RPM lower than with the ZX-12.

To understand how these efforts have played out, it is instructive to read the trilogy of Brock Davidson’s ZX-14 diaries which carefully details his experience with the new Kawasaki ZX-14. After taking delivery of his personal ZX-14, Brock dyno tested the bike right “out of the box” on pump gas and measured 163 HP using a STD correction factor. After 100 or so additional break-in miles, the bike measured 169 HP using the same correction standard. Kawasaki advertises 187 to 195 HP SAE at the flywheel; if you allow for driveline losses of 13.5%, Brock’s 169 HP at the rear wheel squares nicely with the upper limit of Kawasaki’s advertising.

Not content with this awesome display of brute power, Brock set about to wring every possible pony out of the ZX-14 working within the factory envelope. Approaching the task in a methodical manner and evaluating different layers of improvements, Brock finally recorded 191.2 HP on a stock ZX-14 that had not had the valve cover removed. Later he went on to increase this to 195.6 using his street megaphone in place of the BDE Gen III. Much of the increase came from either of the two pipes that were tested, extensive tuning and mapping, use of synthetic oil, use of oxygenated fuel, removal of the air cleaner, installation of ceramic wheel bearings and removal of the “O” rings from the chain.

Interested in improving upon these results Bryan Snyder and I decided to move outside of the factory envelope to further explore the potential of the ZX-14 with the goals of improving peak power, while not sacrificing low and mid power, and maintaining all aspects of reliability. And, just to make it more interesting, we wanted to use all stock parts with the exception of an aftermarket exhaust system….preferably a BDE system…and a Power Commander. Essentially, our platform begins where Brock stopped testing.

With this challenge in mind and drawing upon Brock and Bryan’s experience  with setting-up GSXR 1000’s for the AMA/Prostar SuperSport Class, we developed a list of modifications we felt would work on the ZX-14. We knew we could (1) bump-up the compression ratio through surfacing the head and reducing combustion chamber volume, (2) inspect and reset “squish” height, (3) modify the stock camshaft sprockets and re-degree the camshaft timing to close the intake valve later to better work with the increased compression and (4) port the head to improve air flow through removing factory casting flaws and blending the bowl transition into the throats. Though not allowed in SuperSport, we felt head porting was fair game for our effort as we would still be using stock parts. Unfortunately, installing an intake cam on the exhaust side is not an option as the timing trigger is on the exhaust side.

For our porting needs, we turned to Jason Barnett of Performance Porting in Indianapolis, Indiana. And while there are many good porters in the business, we respect Jason’s approach to porting and have had excellent results with his heads across many different engine designs. He also hand ports which allows for greater cut flexibility and experimentation; hand porting refers only to areas of the port but not the seat. After flow testing the ZX-14 head we had sent him on his new Super-Flow at 28” of depression, it became immediately apparent that ZX-14 head works differently than the Hayabusa head. Before shipping the head, we noticed that the ZX-14 head had a slightly steeper approach to the valve and less of a short side turn to the valve. After rereading some SAE papers and making some phone calls, we quickly concluded the ZX-14 had been designed to create a high level of  “tumble” ……..an in-cylinder motion imparted to the incoming charge. Lower flow with tumble ports compared to high ports is not uncommon.  But because tumble ports promotes high combustion efficiency, Kawasaki is getting more bang for the buck with this design which explains, in part, why their displacement-adjusted torque is 6.5% higher than the Suzuki Hayabusa.

Intake Flow Test Comparison @ 28” CFM

Source: Performance Porting

         Intake Port Efficiency Comparison

Source: Quantum Motorsports

The tables above have been provided to highlight and underscore differences between the Suzuki Hayabusa and the Kawasaki ZX-14 port designs and to present the gains and improvements achieved through Jason’s porting efforts. When evaluating ports, most in the highest levels of engine development look at shape, port velocity, flow, mixture quality and mixture motion. An exhaustive evaluation of the two port designs is beyond the scope of this article, but we will comment on the efficiency of the two ports and the flow and efficiency gains realized by Jason. Efficiency is determined through the calculation of the coefficient of discharge as established by the SAE which provides a means of comparing measured flow to what is theoretically possible. The stock Hayabusa head flows greater numbers at the same lift with just slightly smaller valves than does the ZX-14 which gives rise to generally higher coefficient of discharge measures. The stock ZX-14 is characterized by fairly stable measures of port efficiency throughout the lift range while the ported ZX-14 head shares attributes of both stock heads. It’s easy to spot the flow gains on the intake but it is important to note that significant gains were  realized on the exhaust side of the ZX-14 as well. Parenthetically, port efficiency measurements can be used in determining maximum camshaft lift in a given application and this may proved to be useful in future efforts.

Ported Intake Runner

 Chamber & Re-worked Bowl

After receiving the ported head from Jason, we took the head to our local machine shop to have them mill the head to our specifications. Without angle milling the head, we have found a way to remove more material than what is typically removed in surfacing a ZX-14 head. It takes a second machine operation but we think it is worth the effort as it results in a higher compression ratio. Before reassembling the engine, we evaluated the option of using a thinner head gasket made for the ZX-14 but decided against as it would have resulted in a squish clearance .028” which we felt was uncomfortably close and would more than likely result in piston to head contact. It would have been inconsistent with our reliability goal so we set the squish clearance at the tight end of what we feel to be the safe range. I will say, though, these types of engines “love” tight squish because of its influence on combustion chamber turbulence and combustion efficiency.

When mounting the cylinder head onto the cylinder block assembly, we cannot overstress the need to ensure that the surfaces are clean. After cleaning the surfaces with acetone, we installed the head gasket without applying any gasket sealer. Cylinder head bolts must be tightened with a torque wrench and should be tightened sequentially and diagonally in two or three steps, while making sure that the final reading matches the manufacturers’ specifications. This is a critical step in minimizing potential head gasket failures.

As part of degreeing the cams, we modified the stock sprockets so that they could be adjusted. The factory cam timing is interesting and it is easy to see what the factory is trying to accomplish through their timing and how they are balancing performance goals with environmental concerns.  On the intake side, we opted to hold the valve open a few degrees more than stock to accommodate the higher CR and move the power band up slightly but not so much as to make the bike lazy at lower RPM’s; we changed very little on the exhaust side. Done properly, degreeing cams and checking piston to valve clearances should be done at the same time to ensure that the desired timing is feasible in terms of avoiding piston to valve contact. On the intake side, we like to have a minimum PTV clearance of .050” between 10° to 15° ATDC; on the exhaust see like to see a minimum clearance of .080” between 10° to 15° BTDC.

With the engine installed in the frame and fresh MRX01 in the tank, it was off to the dyno to measure and evaluate our efforts. It’s hard to explain the feelings you experience before your ideas and work are tested; it’s basically a mixture of excitement, confident anticipation and a measure of apprehension. We all know that there few guarantees in life even with careful planning and meticulous work. And, to quote Yogi Berra, “It ain’t over ’til it’s over.”

Because Brock is so experienced and competent as a tuner, we enlisted his help and after some preliminary pulls and a greater number of tuning-link pulls, we eventually got 205 HP STD out of our Super Sport Head package under difficult testing conditions. Just as an aside, this was our target. When examined in the context of Brock’s carefully documented trilogy, we have every reason to believe we are picking-up 10 to 15 HP with this package. The variation has to do with testing conditions, use of different pipe designs, the role of “O” ring removal and installation of ceramic bearings; together all of things could cause Brock’s adjusted baseline to vary between 190 and 195 HP STD. All in all we are pleased with the outcome and feel we accomplished both of our goals of increasing the power limit of the ZX-14 while preserving its reliability. We attempted to test one of these bikes at the track but the conditions were such that could not hook-up and nothing conclusive resulted from our day at the Kil-Kare Raceway. Longer term, we plan to add another layer of performance to this extraordinary machine; while not determined, the configuration could incorporate aftermarket camshafts and or big bore pistons. Bryan may be reached at 937-298-6204.

Steve Swanson
Quantum Motorsports