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Where can I find 15 size pilot jet for my UCAL BS29 carburetor ? Is there any online store or any dealers in Kerala, preferably Trivandrum ?
regards adrian

This is the method I followed to tune my Hero Honda Hunk and the mileage shot up from 43 to 52kmpl!

1. Remove the carb insulator ( thin grey pipe before intake manifold , It covers a brass tube )
2. Now tighten the AFR screw ( Its a 2-3 cm brass colored screw on the carb ) , Note that do not use HULK power to tighten it , use small amount of pressure to just close it)
3. If possible note how much turns u rotated the screw to close it , this will help in reverting in case something goes wrong.
4. Now close the protruding brass pipe from the carb with one of your thumb , If you dont close it , Bike wont idle and it will shut off.
5. Open or turn anti clockwise the AFR screw to 1.5 turns .
6. Now start the bike an set idle to 2000rpm by turning Idle screw ( its on right side of bike , Its a big Vertical screw below tank)
7. Now slowly turn the AFR screw anti clockwise , by slowly i mean 1/8th turn at a time, and wait for 7-8 sec before turning again.
8. You will notice that thr rpm raises as u slowly turn the screw , Dont hurry up as each turn alters the AFR and engine responds to it accordingly.
9. At a point you will see the rpm has gone to a highest point ( mine went to 3700rpm )
10. ON further turning you will see instead of increasing , the rpm drops ( The drop is not dramatic but 100-200 rpm change is there)
11. On further turning you will see the rpm stays constant and doesnt vary ( Stop turning further now)
12. Now slightly turn the AFR clockwise , so that it again shows highest rpm.
13. Reduce the idle to 1100-1200. and switch off bike , reconnect the carb insulator.
14. Drive and see the change in FE and power for yourselves.

This is from Sibun on xBhp. :)

In need of some advice for my Honda Stunner, which has done about 24K kms. The issue is that I used to get an FE of about 60-65 kms per litre in city (yes, that is right) and all filters/ oils have been changed at stipulated time interval or at times, before it too. I use a genuine Honda air filter and have been using Castrol Power 1 Racing fully synthetic oil since the bike completed 4.5K kms. All this while, the bike never returned less than 60 kmpl.

However, since my last long highway trip of approx 1000 kms, my bike's FE has nosedived. It has come down to 50-55 kmpl. I changed the air filter as it was due but this has hardly helped. The tappet have never been adjusted but there is no noise.

I would like to tune the carb. Kindly let me know the correct procedure for setting the AFR specifically to the stunner's carb.

Thanks,
Saket

Saket, you can safely follow the procedure posted above your post. :)

Actually, that is applicable to all bikes with a secondary air injection. :)

Thanks Ashwin. I will be waiting one more time till the bike hits reserve, probably that should happen by tomorrow evening. If the FE continues to be poor, I will try to tune the carb as stated by you. Thanks for posting.
However, there is a doubt. Should we not stop turning the AFR screw once the engine has reached the highest RPM? Your posts says to turn it further. Can you please explain that step.

Thanks,
Saket

You won't know it is at its highest till you turn it a little further and see that it drops. :P

Once you see that it drops, you turn it back. :)

Of course! Just got confused somehow...probably some misinterpretation on my part. Thanks for the tip. Will let you know if I carry out the job.

Thanks.

Haha, mention not fellow T-BHPian! stupid:

And a small tip, just be patient through the process and keep a keen eye on the tacho and wait for the engine to respond to the new AFR before you decide to turn the AFR screw any further. :)

Yes, that reminds me of the time I used to fiddle with the carb settings on my Fiat 1100D!

As I said earlier, I will check the FE until this sunday, if does not returns as expected, I will tune the carb. Thanks for the help.

Always happy to help, Saket. :D

Hi all,
Can any member tell me where is the air and fuel mixture adjustment screw located on a Solex carburetor in a Jonga.I have changed the complete kit which I procured from Pacco India,but now the mixture is too rich and it's giving black smoke and uneven idling.Any Hitachi carburater available?
Regards,

Ask Jaskirat , I think he knows quite a lot about Jonga's. Do provide a picture of the Carburettor, someone might me able to point you in right direction.

Would just like to point out something important while tuning motorcycle carbs. Not always counter-clockwise movement of AFR screw makes the mixture leaner or vice versa. It depends upon the arrangement of carb. If the screw is technically an 'air' screw then you rotate it counter-clockwise to make the mixture leaner and if that screw controls fuel rather than air, you need to turn it clockwise to make the mixture leaner.
The arrangement in some carburetors is such that this screw is located downstream of the throttle valve, in this case the screw meters fuel and opening this screw results in a richer mixture.

Regards,
Saket

Edit: The Honda Stunner/ CBF125 has a KeiHin carb. The Air/Fuel screw controls the fuel volume and not the air volume as it sits between the carb and the engine (& not the air intake). So, turning it clockwise will make the mixture lean and vice versa. So guys, before fiddling with the air/fuel mixture screw, just know what this screw ideally controls in your bike, else you will make matters worse.

Bang on. I used to tune my Kinetic Honda (not the Y2K) that came with KeiHin carb and recall what you say. The prefect setting I found was after running the engine in idle for at least 5 minutes after fully tightening both the Idle and the Fuel mixture screws and turning the Fuel screw anti-clockwise half circle and wait for the RPM to rise. At one point (and this was exactly at 1.75 Turns of the Fuel screw), the RPM reached its peak.

I have experimented this in college days and like you mention, turning it clockwise would make the power delivery very sluggish while turning that anti clockwise would make the Kine zip.

Good old days where I used to ride the Kinetic Honda 54 kms in a day to my college and service it at home.

agree:

4 stroke engines come with a Fuel Screw. This screw, if turned anti-clockwise makes the mixture richer and turning it clockwise makes the mixture leaner. The screw controls the amount of fuel that you are adding to the mixture, hence the name, Fuel Screw. Opening up the screw lets in more fuel and closing the screw lowers the amount of fuel going in.

2 stroke engines on the other hand come with an Air Screw. This screw, if turned anti-clockwise makes the mixture leaner and turning it clockwise makes the mixture richer. This screw affects the amount of air going into the engine, hence the name Air Screw. Opening it out lets in more air and closing it in lets in less air.

Quite simple, yes? lol: