ya..that was what i was confused about..the 9 AH would'nt fi;t..anyways i will wait for some more time with stock..bcos i dont want any mods now..BTW..how does the brakes feel..its kinda spongy..i changes the PADS..Fliud is also fine(no air)..still its spongy..Any idea...

Higher AH battery also needs more power to charge it, a 12V*9aH = 108Watt, so your alternator must generate atleast 120W to charge the battery, anything around 100W is not gonna charge your battery, you will end up with a drained battery and cant rely on it to even use self start.
So stick to 5aH/7ah Battery itself if you dont wanna do any mod and change or rewind alternators.

You can try spraying brake cleaner spray on the brake disc and pads and run few km and see if its still soggy.

If so you need to know if your bike is atleast two years old your brake master or caliper or any rubber parts may have become old and cracked or worn out, also the DOT4 brake fluid needs to be from an unsealed bottle when you are replacing it. You need to get those checked and replaced as well..

Yes,Simply the terminals should supply atleast 14.20V to recharge the 9Ah battery.

Try removing the pads and rub it with sand paper and check once more.

Well..its 3+years old now(42K)..tried changing the brake pads and fluids..but little improvement nor no improvement...anyways i will go ahead and check the options of brake cleaner ...

The pads are new..just 1K Km.I got it+fluid(DOT4) changed last month..

What is the condition of disc plate?

Since the bike's only 42K Kms old the chance of rotor becoming completely worn out is very minimal.

I believe its best to suspect the connecting hose, if its ok then better overhaul the caliper.

yes if you dont want to do any mods then stick to stock rated battery.

a higher AH battery would be needed only if you have plans to convert to dc and to put higher wattage loads like 55/60headlamp. coil rewinding is also necessary to have a higher charging rate..

if you convert to dc with lower charging rate then, a 9ah would give you more time before you run out of power. ie it would discharge slowly compared to a 5/7ah battery and it would get charged slowly also(since its stock alternator)

so, to be on the safer side while putting higher loads, a higher ah battery would be helpful

try this..
i was spraying wd40 on the rusted parts and accidentally it got into the disk and pads, and then the brake started feeling spongy, the bite wasnt there..gave it to service, then the mech rubbed it with sandpaper and the issue was cleared

An totally drained or very less charge held in higher ah battery will give you very less life and less chance to use the small amount of it than an lower ah battery fully charged.

Its like this, having a 6lt petrol tank with 6lt fuel where there is less chance for evaporation than say a higher capacity 25lt petrol tank with same 6lt of petrol where petrol evaporates quickly..
The charge drains quicker and recharges very slowly on higher Ah battery.

Don't ever spray WD40 on chains or brake discs. The WD40 will cause more damage than you expect.

Was the brake fluid properly replaced without any air bubbles? Check this DIY once.
Replacing Brake fluid yourself on RTR180

Less life? How?
brake disc doesnt get affected, but the brake pads absorb it and reduce braking effeciency, removing a layer will help if the amount of wd40 is less, else pad will need replacement.

I just tried cleaning the PADS now need to check the disk...it seems to be in a bit worn out condition-.any clean up suggestions???

They generally lathe the disc to smooth it out but if the disc thickness has reduced, its better to buy a new disc.

Lead acid batteries designed for starting automotive engines are not designed for deep discharge. They have a large number of thin plates designed for maximum surface area, and therefore maximum current output, but which can easily be damaged by deep discharge.
A higher AH battery means more charge withhold capacity, but a poor charge cycle or repeated deep discharges will result in capacity loss and ultimately in premature failure, as the electrodes disintegrate due to mechanical stresses that arise from cycling. Starting batteries kept on continuous float charge will have corrosion in the electrodes and result in premature failure, it should be kept charged regularly (at least once every two weeks) to prevent sulfation.
Which means to charge a 9ah battery on a bike alternator designed for 2.5/5ah battery would mean atleast 5-8hr of riding everyday!

In short its like putting together 3 mobile battery and keeping the charge at 20% when infact you could have kept a single mobile battery for your phone at 100% charge.

Yes, you are correct! The brake pads would need to be brushed with sandpaper, or a good brake cleaner spray too is enough to remove any remaining traces of oil/degreaser left behind by the wd40.

The WD40 will penetrate into the brake pading and the rotor will have a thin film of the WD-40 thingy over it when the pads rub against the rotor hence its better to clean the disc too with soap water and then scuffing the pads with a very fine grit sandpaper.But replacing the pads is a better option in such cases as the brake pads will not perform their best as earlier.

There might be air in the braking system,get the brakes bleeded properly.The rotor will lose its efficiency if you run with worn out brake pads due to metal to metal contact.Replace the disc if necessary.
+1.A good brake cleaner will remove the WD-40,not completely though but I would say replace the pads.

See, consider 2 situations with 5ah battery and a 9ah battery under the same load. A 5ah battery might suffice for the load but it would be discharging too fast compared to a 9ah battery and hence it is the 5ah battery that has got a higher chance of undergoing deep discharge, not the 9ah battery. So which one got a higher life? This chance increases as you increase the load you put.

As you increase the load, mostly it is a higher wattage headlamp the 9ah battery can still provide all the power and can run for a higher time than the 5ah battery before it runs out of juice. You are not running your bike in the night alone right? The 9ah battery will get charged like a 5ah battery itself, but will need a bit more time to reach fully charged condition.

The higher rated battery has got more flexibility than the lower rated one. You are more safe with a higher rated battery.

Sorry. i dont get your mobile phone analogy!