The Bajaj Discover 125M comes with a 125 cc engine, which has been tuned in order to reach 80 kmph with ease. The problem you are facing may be a result of faulty service by the Bajaj Auto dealer and you can visit them again for the problem to get solved. You can ask them to change the filters of the bike or even check whether the engine oil needs to be changed. Your bike is under warranty and you can even claim to get a new bike if you find that other Bajaj Discover 125M with the dealer works better and smoothly.