One more thin i have noticed about this 125cc engine that the gladi has is that the previous bikes that had this engine like the ybx 125 and enticer were not great on the mileage front but were known more for their power at higher revs... Both these bikes used to give somewhere between 45 and 55 as far as i know... Gladiator has a much more refined version of this engine and hence the claim for high mileage...
Well, first thin is 67km per litre what the company claims as tested under actual road conditions is actually not so... Maybe they tested on some highway riding on the same speed for a long time... 55-60 can be said to be proper mileage figures of the gladiator... But if you do intend to extract a lot of mileage out of the bike you can by riding in an extremely sane manner by not accelerating suddenly, keeping below 50 in city conditions and so on... People have said to get as high as 72km per litre doin this... And other 125cc with similar power like the gladi, like the stunner and flame behave the same way... Their mileage figures too are around 55-60 and the tall claims made by the companies usually never show on road...
Not very good mileage... It is highly dependent on how i ride... I have got as low as 35 due to bad tuning... N as high as 58 while riding in a very sane manner... Now it might be giving somewhere around 45-50... Which is also not very good... But i shall rectify that during my next service which is due in around 600km...
One more thing is don panic.If you have already put the K&N u are sure too have these probs till u find the right air/fuel mixture.
One way i would suggest is to take the day off.Take ur bike to a good place.I guess even castrol bike zones if available in mumbai could help u with this.( i don no how good they are in mumbai, in bangalore some are pretty decent). They usually have jets in stock.Try out the same jet by tuning for a better mixture or try out different jets and then tune.Then take it out for a test run.Try running through throughout the rev range if possible in all gears.Check if there is knocking, harshness while revving etc which are signs of bike running either lean or rich.Get back to the service station n check your spark plug,exhaust fumes etc for any signs of richness or leanness.This way by trial and error you can reach at a good air/fuel mixture for your bike.
It might be running lean. I am not too sure.One way to know if it running to rich or lean is to check your exhaust fumes.If there is a very rich fuel odour from your exhaust then it is running rich.
One more way to find out is to check your spark plug.A mech can tel you if the bike is running lean or rich by looking at the spark plug.Or jus google it online n find how to check spark plugs.