Query approved

Thanks alot Noor for approving it. I posted it quite a days ago and thought it got rejected.

i too have a 2010 carb stunner.yes after filling it with 7 litres it shows full.but its ok.but soon it will come down after a some kms.if filled with full tank it will only come down very slowly

You have to remember a bikes fuel tank is designed to not just fill fuel but also adjust for the expanding fuel, due to heat petrol can expand and evaporate, so bikes tanks are designed to hold few more lt. My SZR fuel needle shows full from around 11lt to 14lt. Even worse when you have even 5lt in tank it shows close to empty. This happens in every bike. I really dont bother, all i do is fill fuel when the tank needle comes to 1/4 or 1/2. Its advisable to always keep tank full and not overfilled.

The fuel economy depends on lot of factors. Before you meddle with carb. just do these.
1. Fill full tank normal petrol from reliable petrol bunk (HP, BP, I use Shell).
2. Get the bike serviced once in 3 months. Even if not you need to clean especially the air filter, change engine oil every 2000km along with oil filter, and most imp keep the chain lubricated and brake pads and disks clean.
3. Keep the tyre pressure as recommended and get it checked every 4 days (always check tyre pressure in cold i.e early morning),.

First things first, almost ALL digital fuel gauge indicators are ABSOLUTELY bad at indicating the amount of fuel left.

Why is that?

That's because they use a flotation device for gauging petrol level. This is similar to what is present in out toilet flush tank. In my dazzler if I angle my head enough and use a torch I can actually see the black ball floating on the petrol.

Now this device (in my dazzler) is on the left side of the tank rather than the centre. This means every time I use the side stand on a slightly left inclined surface, I magically get half a tankful of petrol, because all the petrol moves to the left side as the bike is tilted.

Also when I fill in say 7 L, I get a full tank indicated as well (where as full capacity is 12L), this is probably cause the black bob is moving around too much or is above a set threshold level.

Now I have 7 black squares to indicate 12L of fuel and I am sure they are not calibrated linearly or properly cause that would just be plain costly. This is probably the reason why they give you a reserve knob in the first place, cause the fuel gauge reading cannot be trusted anyway!

As far as service centre and mileage is concerned, that is a whole different topic. However I recently improved my mileage from 40 to 46 by JUST changing ONE thing in my riding habit: DO NOT ACCELERATE FAST EVER! Therefore corollary: avoid braking as much as possible. And viola!

So TL;DR: There is nothing wrong with your fuel gauge, this is normal. Please relax!

Edit: This is for digital meters, I do not know how analog meters work but I am guessing they would be just as inaccurate since calibrated and accurate measuring instruments are shit costly as you would know if you have visited any physics lab and asked the cost from the all knowing lab assistant.

Thanks prajnayan for your feedback.
Ya my bike shows Full for around 8L to 13L. It does not show close to empty though when I have more petrol in my tank.
Thanks for the valueble 3 inputs. I follow pts 1 & 2. but I fill air in tyres once in 20-30days as much (PSI) recommended by Stunner manual. The manual says refill your tyres atleast once in a month.
One question... Isn't 4 days too short interval to check tyre pressures? What happens & why is it needed. And for summers since we rarely have 2months of cold mornings...

Thanks for the reply. yes tilting and not having a perfect horizontal display gives wrong result... Generally I make sure that I put the bike on main stand on completely horizontal surface and then check the fuel level when I need correct reading. The analogue meters are also equally bad. Thanks for the mileage suggestion. Wud not accelerate hard.
Yes Iv attended physics lab but did not ask the cost of calibrated instruments from the lab assistant

In physics the hot air expands and cold air contracts,.

So if you filled your tyre in afternoon or after travelling long distance, the air pressure in tyre will be actually higher, and if you set say 28psi in hot condition,. when it cools in night or when parked, the pressure will be lesser now at 24psi, so your bike will eat more fuel to pull your load. Even a drop in 3-4psi will reduce your mileage by 10% or more.

One month is a long time, I usually get it checked once a week or lesser.

@ thread starter,
stunner has got 13L of tank capacity but fuel gauge is calibrated for 10L tank.
I've checked it again and again, and i've filled 13 plus L
Its a design fault.

Thanks Prajnyan for the clear explanation.

Exacty the same thing I experienced. On their site they say 10L but in the manual nothing is mentioned and I filled 13L+ and the bike felt uneasily heavy. The service center guys are confused... How much FE are you getting in city? I am getting just 41kmpl.. The refinement is top notch but the low gearing irritates me as well as the strain felt on engine when driving 60+. What are your experiences Honda_CBF in these regards?

^^Ya stunner is very very short geared. Doing 60 kmph means engine is at 6 k rpm. (stock bike).
But mine is slightly modified (sprocketing).
See, stock cbf (carb'ed) has got 14t front & 43t rear sprocket, having final ratio of 3.071
but i have shifted to 15t front sprocket, so now final ratio is down to 2.867. Which makes my bike run at 60 kmph at 5.5k rpm :-)
but the catch is; its acceleration is like a 100cc bike.
And bike feels stressed only around 5 k rpm, nowhere else but vibrations are there over the most of the rpm range.
.
And my min city mileage is 41-42.
Dont go beyond 5k rpm if you want good mileage along with other healthy riding habits.

Mods, This thread has served its purpose and can be closed.

your explaination neither justifies pv = constant,nor pv = gama . constant.

R u trying to pull my leg here or just having a friendly debate in any post that I comment?

There is nothing to contradict the theory. Ur one line doesnt make sense to me, I actually had to go back to my old study books for this, so here's it for you:

PV = const. where const means PV = nRT ie called the ideal gas law. It holds well for real gases at low densities and pressures, such as atmospheric density and pressure. If we use T = 0 oC = 273 K and P = 1atm, then we find that one mole of gas occupies a volume of 22.4 liters. And this volume changes as temperature changes.

Nothing in the ideal gas law depends on the nature of the gas particles. The value of PV/T depends only on the number of gas particles and a universal constant.

So compared to the pressure outside, the internal pressure is always high which is why if something pokes it bursts, just like a balloon, and this depends on not just pressure*volume but is equally related to number of atoms of gas molecules and the temperature at which it is too.

So effectively a hot tyre will show more pressure than a cold one, which is why you must check correct pressure when its cold and ignore reading fluctuation when its hot..