This is after the “technical hold” in USA and then in UK/EU.
2011 Kawasaki Ninja ZX-10R “technical hold” to be lifted in January
Problem said to be centered on valve spring surge during high-rpm track use
December 29, 2010After causing a firestorm of rumors and innuendo by instituting a “technical hold” on its brand new Ninja ZX-10R literbike (which basically amounted to a recall of sorts, as the 25 or so bikes that were delivered to U.S. customers were offered to be taken back for a full refund) without officially stating the reason, Kawasaki has announced that the hold—now listed as a “sales hold”—will be lifted in January, and “that sales of the highly anticipated unit will resume as normal.”
According to the Kawasaki release, the proactive sales hold was instituted due to KHI Japan engineers discovering that the possibility of intake valve spring surging arose when the bike was “operated under unique riding conditions, such as on a racetrack.” What is valve spring surge? A valve spring, like any piece of solid metal, begins to resonate at a certain frequency. The problem is that when a valve spring resonates, it loses its ability to hold the valve down firmly against the seat, causing a sort of very light valve bounce (this is not like valve float, where the spring cannot even bring the valve down against the seat at high rpm, causing the valves to “float” away from the camshaft lobes, which allows the spring retainers to come loose, which then allows the valves to come in contact with the piston and, well…you know the rest). This poor seating of the valve results in obvious combustion leakage and a loss of power. All valve springs resonate; the key is getting them to do it at a frequency that is outside normal operating parameters.
To the cries of, “why didn’t Kawasaki discover this before, didn’t they test the bike thoroughly enough?”, the answer is that the fact that the bike will be released “as normal” in January indicates that only a certain batch of valve springs were identified as suffering from this malady. Kawasaki says that the intake “camshaft, valve springs, and spring retainers are being replaced to prevent the valves from surging, without affecting engine performance.” Replacing the top end components (or even just replacing complete engines) is a time-consuming task, and you can imagine how long it would take to replace tens of thousands of units that are already in warehouses around the world. Until the bikes that contained springs from this batch were identified, Kawasaki decided to put a hold on all of them.
The following is the official Kawasaki Motors Corp., U.S.A. press release:
SALES HOLD ON 2011 NINJA® ZX™-10R TO BE LIFTED IN JANUARY
Kawasaki dealers to resume sales as normal.
IRVINE, Calif. (Dec. 29, 2010)—Kawasaki Motors Corp., U.S.A. today announced that the recent sales hold placed on the 2011 Ninja® ZX™-10R sportbike is expected to be lifted in late January and that sales of the highly-anticipated unit will resume as normal.
According to Kawasaki engineers, the proactive sales hold resulted from a finding that indicated possible surging of the intake valve spring when the unit is operated under unique riding conditions, such as on a racetrack. The surge could cause the intake valve to seat improperly, resulting in poor engine performance.
The camshaft, valve springs, and spring retainers are being replaced to prevent the valves from surging, without affecting engine performance.
Kawasaki Motors Corp., U.S.A. (KMC) markets and distributes Kawasaki motorcycles, ATVs, personal watercraft, utility vehicles and recreation utility vehicles through a network of more than 1,400 independent retailers, with another 8,000 retailers specializing in Kawasaki power products and general purpose engines. KMC and its affiliates employ nearly 3,100 people in the United States, with 300 of them located at Kawasaki’s Irvine, Calif. headquarters.
Kawasaki’s tagline, “Let the good times roll.™”, is recognized worldwide. The Kawasaki brand has become synonymous with powerful, stylish motorcycles for over four decades. Information about Kawasaki’s complete line of recreational products and Kawasaki affiliates can be found on the Internet at www.kawasaki.com.
Source: Sport Rider