I bought a scooty pep in 2006, it hardly 3 years - here are experiences:
The mileage drastically fell down to 25Km/Litre
I had to take to repair shop once in every 15 days
*Astonishingly, I had to replace the piston and engine components
*Even the authorized service personnel/dealer replaces the battery and royally screw you. Every time you take it to the show room, they will show some weird problems rob you.
Thrice it stopped in the middle of a busy road.
Once due accelerator wire and there is no service center around. I finally had to leave it with a nearest repair wala, take a lift and go to the showroom to purchase replacement cable, came back and got it replaced it. The whole saga killed my entire day.
After 3 days, the cable got stuck, the bike is continuously raising(accelerating) and became uncontrollable -- and my sister rammed the bike into the petrol station. Thank God, she is spared without major damager. When inquired, the problem is the faulty sparepart sold by genuine TVS dealer ;)
The fact is, the parts manufactured or marketed by TVS are very poor in quality. As a result you can never rely on any part including the piston !! And hence there is always a risk that any part can let you down any time.
It is sincerely an unreliable bike!! It can stop working any day due to any stupid reason.