Re: honda stunner mileage prob Help required

Hi I am Chinmay
I bought Honda CBF Stunner in 2009. I've recently been having mileage problems with my bike. Though I also had a lot of work in the engine too and the engine is almost new. But I'm having mileage problem since then. And a very strange thing is that the authorised mechanic of honda does a road test for mileage after fully emptying the carburetor fuel, and giving the fuel supply through a bottle containing 100 ml fuel. In this test, my bike shows mileage of 65-70 km/lit. But when I'm actually riding the bike and filling the fuel tank the average is way too low than that showed in the road test. It around 22-25 km/lit. And also the bikes feels very heavy to ride. As if the acceleration is not free.Honda mechanics are not knowledgeable and everytime they do this setting that I'm fed up of. Looking forward to help from you people.Today only I checked my bike's mileage via reserve to reserve method. It came 30-33
Thank you.

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And I want to tune up my carburetor myself. But I don't know which are fuel and air screws. So if anyone could help me posting a picture of carburetor with fuel and air screws highlighted, that would be a great help. And also tell me how to tune. I'm an beginner in this.

Re: honda stunner mileage prob Help required

Hi I am chethan.. i joined the forum recently... the fact the keihincarb is Honda service standards for carb air screw says so for stunner,shine(1.75); unicorn(1.5); dio,activa,aviator(1 for 100cc & 2 for 112cc engines respectively) for further details on keihin carburators u can also refer to http://www.keihincarbs.com/tips/gate.html
have a grate time guys

How-to: Check and adjust valve clearances on the CBF125 | CBF125 Rider there's also a video on YouTube on the same. Try searching for it. Couldn't post it using mobile, sorry..

HI,
Honda service guys are not knowledgeable at all....tats wat i felt ... I dono if its the same in other Honda service centres....
I asked the service guy to tune my bike.....he kept it 1.5 turns... Oh god....since den i had no pick up, engine overheating n alll...
finally i had to tune myself.....

By the way, at how many turns from closed position have u kept ur AFR screw at???

The new shines and stunner are coming with this problems. Almost all shines complain of low mileage.
As far as my knowledge goes the new bikes from honda are coming with very poor quality checks. So most of them have valve problem which goes on leaking compression.
In the middle there were some batches of extreme suffering from same problem. But latter it was corrected.
I think stunner and shine are also suffering from same problem as many are complaining of the same thing.
The solution is to open the head and valves and polish the valves and set the tappets.
The mileage will be back to 60-65.
With the increase in production and automation in production, this is what happens.
Quality has gone down the drains. Mainly because of:-
1. Cheaper pricing as customers are searching for VFM rather than quality,
2. Huge production and thus less time for quality check .
3. Automation. When everything is automatized a single problem will get repeated until manual intervention is done.
So just open the heads polish the valves and refit, your bikes will run better than new.

Hi mate,
my stunner has done around 5.3K kms. I too am getting mileage around 40kmpl. I tuned the AFR screw myself what I felt was optimum. Gotta calculate again. I believe Stunner has a habit of going into high RPMs quite quickly thats why its milage is very poor in the segment. I asked Honda service guy to replace the front sprocket with that of Unicorn but he simple said thats not possible. Next time I would go to a local mechanic for servicing, they are better and more helpful than Honda service guys. He might increase my mileage

Hi,
Thanks to all that info....great..
i have done 12,500 km on my bike.... as u said i don see much change in mileage because of the carb tuning... currently im running at 4 turns after trying out many.... mileage is around 40 - 45...
By the way how to check valve clearance?
sure, ill check for carbon deposits on piston...


thanks

Instead of fiddling with air screw find out if any other systems are at fault.
Simply fiddling with carburettor is not recommended.
If your engine is feeling like running rich then it may because of lose in compression.
There are many other factors responsible for low mileage and pick-up.
So i will tell some procedures starting from simpler to more stricter:-
1. Spark plug and air filter ruled out as you have changed it. However, i do not trust NGK plugs and have suffered many problems with new plugs.
2. Carburettor- Clean the carburettor. Slight dirt anywhere, be it in the idling circuit will cause low mileage and tuning problem. See CBF's guide in DIY section. Open the air screw and check dirt on the tip and also check the o-ring.
3. Check tappets and see. We check tappets when they sound on becoming loose. But when they become tight we cannot know. So check with feeler gauge and see if they are tight which will loose compression.
4. Open the spark plug and move the piston to TDC. Through a torch check the head of carbon deposits by peeping through spark plug hole.
If there is excess carbon deposits then open the head clean it and also polish the valves.
The new engines like unicorn, stunner, activa consume a bit amount of oil always. Unlike the old engines like splendor, karizma e.t.c they do not completely stop oil into chamber and thus cause quick carbon deposits and bore replacement as early as 35k. Shine and Stunner engines are well known for it.
So check head carbon deposits.
Regarding the early carbon deposits, it is no surprise as new engines comes with softer rings to aid in low consumption of fuel, less wear on bore, no engine seizing even under hard ripping at run-in, engine revving quickly.
But the downside is that the rings loose tension easily and thus require early replacement. This is the cause for early carbon deposits in present engines.
Want a proof:-
Find two motorcycles like splendor and shine or CB twister. Both should be new pieces. Now kick both, in splendor you cannot kick and will have to exert very hard pressure. Some times you just cannot kick from full up position. Now do the same on new engines, you will feel it easier.
Heck the difference become more at 20k.
So most present engines suffer from mileage problem due to valve problems and carbon deposits. I have seen valve problems in new shines from showroom.
A good decarbonisation and polishing of valves will sort it out.

But first clean carb and check if choke is not slightly engaging.

In my joy even after so many kms the kick feels so hard in compression stroke that i cannot kick sometimes and i meant it as i squat in gym with a 60 kg barbell. So you can know how hard is it.
So check all the points and report back.

By the way how much KM?

I hope you have taken care of other factors too as stated earlier. Also there have been reports of increment after getting the valve clearance (tappets) adjusted. For tuning, you can also try for 1.5% of CO (carbon monoxide) in exhaust gases.

Hi....
Initially i tried with 3.75...but my mileage wasn't tat great...it was around 40....den i tried with 3.25, den mileage it reduced even further....
again i tried at 2.75.... it was ok ok...engine was getting heated up with mileage less than 40....

finally i realized with trial n error that my optimal setting is between 3.75 and 4.25.... currently running at 4.0 turns... its pretty smooth at this setting and not much heating....checking for mileage now with 4.0.... will update soon as possible...
i tried to tune also..the rpm was fluctuating below 3.75 turns....it remained constant at nearly 4 turns... so i have decided to keep it at 4 turns....
wil update soon

Any update mate??

Hi,
Its a fuel screw... if u turn it clockwise, it makes it leaner.....anticlockwise it makes it rich...

Thanks.

Is it fuel screw or the air screw?

Yeah. 4 turns is what bike just loves. Psr ji also suggested the same when I had carb tuning issue. But de-tuned it at 3.75 for mileage.http://www.xbhp.com/talkies/help-me/...g-stunner.html that's the link of the thread. Hope it helps..

and after tuning don't forget to turn the idle down to normal. i think 4 turns is a rich one though i believe there is no universal setting for every same model. each bike has to be tuned for itself. try out and post. happy tuning.