Well well well... wanted to post this observation as soon as we were back from the ride but I had to rush to office
When I was riding back and leading the group, I did the max speed of 161 or so on the speedo Abhinav and Harsha were coming behind me more or less maintaining the same distance and they have mentioned to touch the speeds of 170+

Till 5th gear @12krpm the maximum speed my bike could attain was 145kmph!

Coming to the max speed that could be shown on speedo for my Ninja if at all I red-lined in all gears (which I didn't) I suppose it might reach up till 165 max.

No idea whether it was speedo error with previous models or with 2011 model.

We can do the following to check the correctness:
1. Check with a couple more 2011 models against the previous models
2. Check the original speeds with a bigger bike as a comparison
3. Source a speed gun if possible (Was just browsing to find out that there is a Speed Gun App for IPhone)

Edit: There was no chance of clutch plates slipping... Coz we are cent % sure that we were doing same speeds

We first noticed this when the first 2011 bikes started coming out about 6 months ago - on the tristate g2g, Whizzkid's 2011 bike was keeping up with three 2010 Ninja's clocking about 170 ( on our meters ), yet his kept showing about 15kmph less.

I would say definite speedo error, though I don't know which one is accurate. ( though I suspect the newer bikes to be accurate )

As for the 'drop' in the 6th, even at high RPM - I 've noticed it too - the bike seems out of steam by 12K at 6th while the older bikes seem to be able to still have some left.

What you guys can do is check the free movement of the speedo cable. See if any play or anything.

You can use a GPS based cell phone even to confirm the speeds ( Using an integrated GPS enabled phone will be better than A-GPS phone ).

Remembering the Ninja rides!

Met this police officer in California and had a lively conversation about our ninja rides back in India.

Also met another fellow rider with his travel buddy!

Yes, I plan to do just that soon. Would want to test it all the way up to the redline but atleast 11K would be the target. Thanks for the tip.

No, I haven't had a chance to ride another Ninja except one I rode during the test-ride before purchasing. Talking of the test-ride, that was a pre-2011 model and I remember touching 150 KPH easily without even trying hard at all. Mine is a 2011 model. If I think back now, the speed didn't actually feel like 150 but I was all smitten by the Ninja and just happy knowing it could go so fast without effort that I didn't pay too much attention to the doubt. And then, I had never ever been on a bike that could do 150 so I had no benchmark to compare against. The same speed in a car and a bike "feel" totally different so that was not a comparison and I just let it be.

I am feeling more convinced that there could be a speedo difference/recalibration between 2010 and 2011 models. However, I still feel my bike should give me some more than what it is doing right now. Even with the speedo difference, I should still touch 150 atleast. I might just go down to the dealer and take the test-ride bike for a spin again to get a comparison of sorts.
Let's see how it goes. I will post back my findings.

If you're a Mumbai resident then I can possibly help you with the speedo error bit. Do let me know.

Just FYI., 165 on the speedo on a 2010 Ninja 250R showed 159 on the GPS.

Damn! That bike is FAST!

good to know that the error isn't 15kmph! error less than 4%

It's surprising to see speedo error to such an extent of 15KMPH.
I haven't compared my Ninja with another Ninja but will be doing this weekend but it will also be 2011 Ninja.
Went to PBK yesterday after lot of analysis on what could be the issue behind all this and was now suspecting a clutch slippage as I zero down all the possibilities for this before.
The regional manager was there and he too felt slight drop in acceleration and felt it could be due to clutch slippage. I was getting really feared of by this as my new bike would be opened but he was a knowledgeable person and assured me that it is just a check and everything will be done under his supervision.
So, the clutch plates and pressure plates were checked and found that there was carbon deposits on it which could cause slippage. The plates were cleaned and the bike was packed and wash was given. I went for test drive after that and found difference in rpm vs speed, it was now nearing to normal as before. Could not do a high speed check due to city traffic, will do that this weekend but a dyno check that time and found it was a better than before.
Also, had long chat with him regarding the oils that can be used for Ninja 250R. He told that Kawasaki has not recommended fully synthetic oil for this machine only mineral is suggested by them but semi synthetic can be used as it comprises of 70% mineral only. He told that if they have suggested us to use fully Synthetic then we would have definitely use in this machine.
He said you can use any brand of mineral oil and it will last the specified time interval of 6K easily but it should be meeting with the grade.

happy to note the improvement after clutch plate cleaning....any JASO MA2 certified Mineral oil of recommended grade will work well.
As recommended by the RM..... DO NOT USE SYNTH oil
Change the Mineral oil every 2,000 Km and you will have a clean and happy to rev engine.

145km/ hr max on 5th gear, that is strange cuz ceeber does 143 km/hr on 5th. The speed errors would be different I know but I was all set to get a 2011 Ninja. Other 2011 Ninja owners should be checking this figure to spot the difference out.

I stay in Hyderabad brother

Good to know that your problem is resolved
Mineral Oil for 6k sounds unreal buddy considering the high revving nature of ninja.
P220 owners using Bajaj 10k oil were saying that the oil was loosing its life at around 2.5k kms
Using mineral oil/semi synthetic is Okay but i would strongly suggest to regularly check the oil state regularly (though color is the only thing we can see from outside)

The bike might be going at a higher speed or lower speed at that time Speedo errors are pretty possible
We can't comment unless we do a high speed run together on both the bikes
My Karizma used to show the maximum speed of 145kmph on speedo where as R15's used to overtake me at a speeds shown as 130kmph on their speedo

*** No offence meant to the CBR.. I love that bike too (A lovely commuter and tourer ) ***

lol, it was never a comparison, I know Ninja is mighty enough, for that only I wanted you to get it confirmed by riding other 2011 Ninjas. This would at least bar you from living in assumptions.

Cheerz buddy.

It was! Just like you mentioned!

I went on a ride covering 1650 Kilometers in a day (which they call saddlesore), the gps odo showed around 1627 !