The top speed is not drastically different with -1/+2. You aren't actually going 255 kmh in the first place, due to factory error. You might lose 10 kmh or so.

 

To correct my speedo with the -1+2 I had to change it by 16.9% total - I do not know what the factory error was. So if you're doing actual 255kph (159mph)(which we know you're not because of factory error) you're going to lose about 43kph (27mph) of that to bring to about 212kph (132mph).

Here is a speed/gearing calculator. Just enter your machine info and it will load the factory gearing then you can change your sprockets and it will calculate everything: http://www.gearingcommander.com/

 

Well, i have the OEM gearing so i was infact at 255...if you put -1+2 your top speed has to be less than having oem.

 

Speedometers have a ~5% error from the factory, so it's unlikely that you were actually going 255. An incredibly accurate GPS or radar gun is the only thing that will give you a for-sure reading, and that's how most people figure out their percentage for a speedohealer or similar product (that and the gearing calculators that are out there).

 

I'm agree with you BUT that's when you have modified the gearing... there's a youtube video of the F4i top speed, it shows 273 km/h so why not me??...

 

With OEM gearing I believe by-law they are allowed to be off by as much as 10%.
My OEM gearing is off by about 5% when reading from a GPS.

 

No, it's not, that's why I said from the factory. Just because it SAYS that doesn't mean that's how fast you're actually going.

 

John Cu- I have never been n any motorcycle that the speedometer was correct from the factory. They will all be off anywhere from 5-10%.
Check that link I posted earlier, it will show you.

Even car speedometers (except police and very few others that have been certified) are not exact. Most will read 1 or more mph higher.