Actually I was surprised by mileage being given by Twister, as I am driving it in range of 20 KMPH-40 KMPH ( not mileage friendly range for any engine ). Mileage in range of 40 KMPH-50 KMPH would be big surprise for me .

RPM meter is mounted on one out of two bolts of bike handle. I will post pics soon...

Actually 35-55 gives the best mileage.. so you are within that range and going to 40-50 wont improve it for more than 5kms per litre, but speeds over 55 reduce the mileage a lot, that I know

I am within that range only for say ~ 25-30 % of time. Even if it improves 5 KMPL more...I will be getting around 82 KMPL . Short story....I went to get oil changed at local mechanic. There a person was interested in enquiring about twister, He asked me mileage. I said its around 75 KMPL, then he said " Yes..companies claim these kind of mileages but what is actual you are getting ? " I said " This is not company claimed, but actual mileage I am getting" and he was surprised .

Why mechanics, even friends get amazed I say 70 as mileage so that little ripping takes its share

Bro,don't forget to post your bike's pics,& also try to make it at the earliest.

But if we use a electronic flasher which supports 0.02amps to 10amps then this issue will-be resolved. At these speeds you can even get more-than 80+ if you use a correct gears. It's purely depends on driving style only.But there is no much more difference in mileage at 45 to 55KMPH Even my friend having twister but getting only 60kmpl, he's scolding me like "how can your bike give 75+kmpl"

How much does the mileage depend on the number of kms the bike has done ? I have a Dream Yuga and Im not getting anything more than 50kmpl and when i complained during service i was told that you have to complete atleast 3000kms on bike for it to improve mileage ( have run 2.5K right now) before the mileage can improve and was told that the mileage is low because its not run 3-5k kms

No bro.. It only depends on how they tune the carburettor. Some sc pople are so lazy to do it. Another thing is how you drive it. Lots of stop and go, city driving requiring constant revving and downshifting, then 50 is normal. above 70kmpl is only for 70% highway and 30% city driving and that too at 50kmph speed without deep acceleration and revving. Needs practice.

As joseph said it's purely depends on driving style+driving condition. If both are good then check the carburetor else no use in it.

Thanks Joseph and Rajaselvam
I also had this wierd problem after 1st service : Whenever i left the vehicle idle for some time ( say at a signal) for ~1min and then rise the throttle the vehicle used to behave as if the fuel was cut off and then switch off ( similar to what happens when fuel is empty and vehicle is about to stop ) and then bike wouldnt start immediately and i had to kick start after 3 to 4 failed attempts and it would start again, I also observed black smoke if I raised the throttle after leaving it idle for some time, This issue did reduce its intensity after the 2nd service and the bike seems to be better in that it doesnt switch off if i leave it idle and start moving but i do feel that power loss when i open the throttle some times ( not always ) but the mileage has consistently stayed at 48-51kmpl even when i had the issue and after the issue was fixed, Im starting to think if this is related to carburettor setting, any comments from experts would be helpful , could there be any other reasons for this behavior ? electricals?

Mechanically, there are 2 adjustable things on this bike which can affect fuel efficiency. The first is the carburetter Air-fuel ratio screw. Initially your carb would have been set for a rich fuel ratio, that explains why it had more power and now after making it lean, you are feeling a loss of power. But black smoke is a serious trouble with valve clearance. No setting on the carb produces black or white smoke. So I guess first you should get the valve clearance checked. Next get the carb tuned properly. A rich mixture means more fuel and lesser air and will give more than normal pickup and power but low mileage. A lean mixture means more air and less fuel, gives excellent mileage like 80+ but very low power. Making too lean could damage the engine after a long time due to overheating. So make it a bit leaner than normal but not too lean to get a good mileage. Making it lean also makes the engine shut down frequently when revving after idling, so increase the idle rpm a bit higher to avoid shutting down at signals. Maybe the service centre people you are visiting are not that good or otherwise they are too lazy. If you can, try another service centre and get these 2 things done.

Also check the operation of choke lever....it may have been left half open or fully open which will put excess fuel causing black smoke.

The first thing i checked was the choke but it was in off position so that doesnt seem to be the reason for black smoke
The Carburettor setting rich or lean seems to be a little confusing in my case, when i was facing the shutdown problem ( lean mixture ?) i was getting the same 50kmpl so it doesnt seem like it was set too lean, Also Nowadays i feel the engine is running hotter ( running lean ?) now but Im getting less mileage and the area near the oil filler cap seems hot enough that i cant touch it after running for 5-6kms
Is it possible that if some sparks are missed due to fault in electricals it can cause low mileage ( because the fuel is not burnt in that cycle) ? During the first service when i had complained i was asked to take back my bike to service center for this issue and the service guy removed the wire connecting to spark plug and was runing the starter motor and testing for sparks flying from the wire end to engine ( ground) and said that some sparks were missing in between and he needed to replace some coil and check, sadly that coil never was in stock and i was never happy with that guys explanation so never got it changed

probably he was talking about ignition coil which is responsible for creating spark. if its weak or faulty then that could be the main reason for the problems you mentioned...like taking many attempts to start.....but they should replace it free of cost....as its covered under warranty....its costing 500-600 Rs. by the way 50-55kmpl in full city condition is normal mileage.....i have read Dream yuga reviews in magazines such as autocar and overdrive...they also claim mileage of around 50 kmpl under city riding conditions. my twister also gives 55kmpl under traffic conditions. check this review below....it claims 47kmpl mileage for DY.
Hero Splendor+ vs Honda Dream Yuga mileage test - Overdrive

As sachin said, you should get it fixed under warranty if that seems to be the problem.. but sparks missing is easily noticable. There is only 1 spark per rev and if it misses one, it behaves like petrol is about to get over getting jerky. Missing sparks could be due to a faulty spark plug, a faulty cable or ignition coil or CDI unit. Best wud be to visit another service centre and get everything checked.