First of all what is the back problem!? Back problem could be because of many reasons.. Have you got an x ray done. If it is originating from the spine get yourself checked. First change your doctor then your bike. My friend had a similar problem and he was thinking of changing his bike until he came to know that he has got a herniated disc. Read more here - Herniated or Ruptured Disc - Cedars-Sinai
God forbid, if you have got something like this.. please discontinue biking.. Your old santro or a new nano or any other car is the only way out.

Secondly, if you are just getting pain from the jerks on road after riding your bike - get these things checked.
1) Check the height of the handle - During service the mechanic may have adjusted the height causing your bike to lose its usual posture.
2) Get the shockers checked. Not only the rear ones, but the front ones too.
3) You may be overfilling the tyres or the tyres may have got hardened (of age).. ride with optimum air and not 35 front and 40 rear as is always filled by the petrol bunk operator. You may even look for wider tyres - Wider tyres provide much more cushion. Your bike comes with bicycle tyres.
4) The small seat on your bike may have got hardened of lost its cushion.. getting a thick cushiony seat cover may be tried.
5) After consulting a good doctor.... start exercising (especially the lower back movements)

I dont think you need to change your bike as the bike you have is quite comfortable. Roads in Mumbai are not so bad! ;-)

To get something you have to lose something!!

Nothing can be best as a car regarding comfort!! Get your old santro on CNG and use it!! Old Santros or old Zen are awesome on CNG!!

Add another one to this list. The Hero Impulse.

Also Somen has a good point too. Santro + CNG might turn out cheaper overall than spending 60-80k on a bike and then living with 45kmpl of Petrol.

thanks muztariq
I drive with the recommended air pressure written on the bike . 41 rear , 25 front. Now should i change this???. As you said the tyres could be the problem as they are nearing its life and i was avoiding changing considering i was going to sell this bike. But if that could help I can try. I will go for a little wider tyre.The shocks and handle have been tested. The mechanic said the shocks are fine and it is not required but if i want i could change the front shocks oil.
I might change the seat cushioning.

As regarding cng plus santro ... the santro is little too old for that and buying another car is not within my budget yet.What i can do is start driving car plus bike 50-50 instead of 20%car and 80% bike which i do right now.
Thanks a lot again all of you guys..

Firstly, fzs/fazers wont provide 45 kmpl in city, but on highways you may get that. I'll suggest you to go for yamaha sz-r. Suzuki gsr is also a good bike, but its big figure and heavy weight don't let you a zigzag fun in heavy traffic. But on highways its very good. So choose between the two. Their is another excellent bike called Pulsar150, but you have to take care of it very well for long-term usage.

If ride quality is bad, changing the whole bike is not needed. Instead, first do an overhaul of the seat (get more cushion and foam padding and enlarge it) which should cost at most 1k. Then switch to softer shock absorbers. Ask around good mechs and they'll be able to tell you which shocks are compatible with your bike and how soft each one is.

Anyway, for me personally, only a seat overhaul was enough to eliminate serious pain in my butt while sitting, sleeping, etc. So yeah, do try out simpler alternatives instead of ditching the whole bike.

Take up the less costly items first..

Front fork oil change.
Reducing rear tyre pressure
Seat with cushion.
Changing the height of the handle.

Rear shock replacement and wider tyre installation for later.

Don't know why but i din't find D125ST's comfort something different then normal bikes??? infact Dazzler or ZMA etc are more comfortable then D125ST to ride.
This won't give you any help, infact it will increase your petrol and maintenance cost.

If your car is 15yrs+ old then only you won't get a new license for CNG kit, But you can find second license CNG kits.
Mostly i have seen riders growing weight is 80% responsible for back ache on bike or in other ways.

Few of the people whom i know in which there are heavy weights also there, are more complaining on back aches with bike comapre to thin under control weight people.

You have 3 ways according to me.. Buy a new bike selling your current one.. And from my experience zmr is comfortable but until you get used to it, it may seem bulky in traffic which may pose as a trouble to you.. So neglect it if you feel so.. Else the Karizma which may or may not get a make-over.. No idea.. The hunk is the next best option solely due to GRS shocks which are better than nitrous ones.. Else cbr 150 would be good due to its riding posture..
The next option is modify your current ride.. I have no idea if you can replace your shocks and change the angle of your handle bar.. But if it is possible then do that first instead of buying a new bike..
Last and best option would be to use your santro.. Health is important first.. Then consider your expenses on fuel!!

Thanks for all the input.
Considering my low running.. I have made a decision to make a few changes and use this bike.

1)I am going to change the front shocks oil as this is whats causing the ride to be bumpy according to the mechanic.
2)Rear tyre pressure reduced to 35 from 41. front is still 25.
3)I have tried to correct my posture now and sitting straight while wearing a belt which supports my back while riding.
4)Will ask the seat guy what he can do about adding more cushion to the seat.

Just a side note, just like any other human being i got a little excited to change and get a new bike.Thanks for talking sense into me and making me realize its not really needed. I can use this bike at least for another year and it has really been and awesome no trouble commuter bike.

If i feel any improvement, my tyre which is almost worn out i will replace it in a months time.

Hey Bro hoe come CBR is more comfortable then a ZMR ?? CBR has more front leaning position as compared to ZMR or ZMA.


If your condition is really so bad that you need a belt to wear while riding then it's better you use a car or RE/ZMR only rather than your upgrades or mod on existing bike!!

Remember just saving petrol expense should not be the moto, It should be your health, Once if you get caught with Slip Disc etc then your life will become hell!! So think wisely. If a new bike then take TR for good kms of 5-6kms.

No no i was just giving a list of bikes with comfortable riding.. I did not mean cbr is more comfy than zmr! And also i tried mentioning them according to priority so i felt it was zmr, zma, hunk and cbr thats it..

Ahh!! I was thinking the same!!