Now that is the right thing you have mentioned bro.. If they don't respond to my problem and don't replace it i will definitely do the above mentioned thing. Is there any thing else that i should tell them or i should do.

Just follow what PSR JI says; he's subject matter expert on these. Worst outcome will be YMIS will refuse to accept that its a failure in master cylinder for which you've to do some smooth talking & make them accept its manufacturing defect.

Thank you PSR,argee,Gyroerror,soumen for the help. I will inform what happens next..

This is a standard reply Raj Even if the issue doesn't happen in front of the ASC people, you need to stress the fact that it is a life threatening problem and you need a complete replacement of the master cylinder or due repair (as PSR suggests). I had a starter issue wherein the starter condensor (or capacitor) wouldn't work after long distance travel (or more vibration). I had to tap it or hit hard some times to get the starter working again. I was not able to show the issue in front of ASC guys but convinced them that I could be stranded at any dark road without fixing this. They had no choice but to replace it under warranty (may be because they had a bad experience with me when I escalated few cases to Yamaha area officer)

Also, I would strongly recommend a proper brake fluid bleeding. Seriously Yamaha ASC guys doesn't know what is meant by brake bleeding. They fill oil in the master cylinder and keep pumping the brake after closing the bleeding nut till their satisfaction. Refer my other post in Drifty's brake-fluid-replacing-brake-bleeding-rtr180#post819200 thread.

thanks brother for the help...

Another problem could be that the seal/spring under the fluid container (near the brake lever) has malfunctioned (is this the master cylinder that PSR ji is referring to?). This happened with my motorcycle. My mechanic replaced the set and now, the brake lever does not go all the way, but engages on a slight press.

We had to spend 2-3 days figuring out what the problem was though, my mechanic was kind enough to open up the brakes, check the liners, oil the pistons (just in case) and also drain and put in new DOT4 fluid. Once all that was done, I still faced soft/spongy brakes, as well as the lever depressing all the way to the accelerator. Having ruled out other issues, he replaced the set under the rectangular brake fluid box and it was solved. I also suggest following PSR's advice, so as to cover all scenarios.
In the worst case, get the entire brake set (from the box to the pistons) replaced under warranty, you are entitled to that.