I have purchased 2805 1400 kv motor from Sai, he says it is 1400 kv motor but on other site I found the same motor they also says 1400 kv motor in main  title but when i read it's specification it is described as 2840 kv so i am confused which prop shoud i use for this motor?

http://cgi.ebay.it/New-RC-Timer-2805-14-1400KV-Outrunner-Brushless-Motor-/120472140154?cmd=ViewItem&pt=UK_ToysGames_RadioControlled_JN&hash=item1c0cb2f97a

Both sites say 1400 in their item name/heading.  Only the italian site seems to have made a mistake of putting a wrong KV value in their item description. 

If Sai has confirmed it, end of story !  Plus the size and shape does not look like it is a high KV motor (although that can be misleading).

Even i think it is 1400 kv. As far as i know Sai uncle will never make a mistake in the specifications.

In any motor the KV can be  changed by changing the windings .
The Motor was first produced by the manufacturer with 2850 KV,

We then got it  rewound by them for us to 1400 KV   for use in Mr MOSS  , so we have sold  over 300 of these motor with 1400 KV  and have comfortably used upto 9 " props on them  in fact we also used it on a piaget with a 10 " prop  on 2 S .

Hence  the motor supplied to you is 1400 KV .

Sai