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The U.S. version of the ZX-10 will not win Track tests or Drag runs against the S1000RR.
The lack of power will put it behind in performance tests, might do good as a street bike.

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The U.S. version of the ZX-10 will not win Track tests or Drag runs against the S1000RR.
The lack of power will put it behind in performance tests, might do good as a street bike.

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Couldn't agree more. It is heading for a sales flop unless the recall magically upped the HP. The majority of the buyers look at that HP number as their #1 consideration. Doesn't matter that you can buy parts to unleash it, you can do that with most bikes. They want to jump on and have what they need, and with the stricter laws about modified exhaust it is only going to get worse.

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I might put one next to my Beemer if it made the same HP but was lighter.
The weight they are claiming is equal to the CBR1000RR,very light ,but being
20-25 ponies down is a deal breaker.

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U.S. bikes will dyno 20-25 ponies less than BMW

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The long mystery sales hold on the 2011 Kawasaki ZX-10R is scheduled to end in late January, and the company has given an explanation for the holdup: the possibility of intake-valve spring surge (coil vibration) under what Kawasaki calls “unique riding conditions, such as on a racetrack.”

The intake camshaft, valve springs and spring retainers of new ZX-10Rs will be replaced to eliminate this possibility, “without affecting engine performance.”

Computers are wonderful tools, but physical testing continues to be essential for critical performance areas, such as valve-train stability. Valve-spring surge is the rapid bouncing of a wave of compression from one end of the spring to the other. It is excited by very rapid cam acceleration. Surge results in a swift variation in spring pressure acting against the spring retainer, which is fixed by a pair of tapered collets to the end of the valve stem. This pressure variation can result in the valve’s failing to accurately follow the cam contour, or, as Kawasaki’s press release words it, “The surge could cause the intake valve to seat improperly.” Improperly means hitting the seat at too high a speed, leading to bouncing and damage.

Every manufacturer must deal with the possibility of surge, beginning with a computer model, moving to rig and dyno tests, and finishing with road and track mileage. Spring surge is very speed dependent, so much of an engine’s defense against surge comes from the fact that, in track use, rpm is constantly changing—never holding constant at the one particular speed that makes surge most likely. I suspect that Kawasaki discovered a possibility that surge could develop if rpm were held at one particular high and constant value, and decided to withhold the machines from sale until even this possibility could be eliminated.

The new cam may be subtly reshaped to suppress surge, the new springs may have a different natural frequency and the new retainers are most likely required because the new valve spring length is somewhat changed. All these changes can be accomplished without affecting engine airflow—or, as the Kawasaki release says, “without affecting engine performance.”

People are expecting a lot from this new ZX-10R on both street and track, which motivates Kawasaki to ensure that they are not disappointed.

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Thanks Fish....found it in some other threads as I read through....if its valve springs, and valve train related why would KHI take back the bikes already sold instead of just doing a recall and replacing the parts that are faulty? doesn't seem like a smart move to me.

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Thanks Fish....found it in some other threads as I read through....if its valve springs, and valve train related why would KHI take back the bikes already sold instead of just doing a recall and replacing the parts that are faulty? doesn't seem like a smart move to me.

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Probably because they have no way of knowing if there has been any mild damage/engine wear already. For example, there could be some contact of the valves and pistons, or maybe even damage to the valves or seats....that sort of thing, which would possibly show up as warranty claims later. To fully inspect these engines, you would have to pull the heads. That could get really expensive, and they probably did the math. In the end, it probably comes down to money.

Just a guess?

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i've been out of the loop, has it been fixed? is the north american version running like the euro?

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