The carburetor is tuned by monitoring the exhaust CO levels. Most of the medium level service facilities have this instrument. Although 3rd party engineers can tune it by measuring the exhaust gases, nothing can substitute the factory state of tune.

Exhaust CO(carbon monoxide-a toxic pollutant gas) is monitored by the same equipment as is used by Pollution Testing centers for issuing the mandatory PUC certificates . Almost all bike/car ACSs have these( they use it for issuing PUC certificates ) . If your engine is emitting CO in excess of the mandatory limit for obtaining a PUC certificate , they'll tune your bike to pass the test then .

How do they tune?

By adjusting the carburetor to a different AFR setting .

Have seen this being done. They make the bike run lean to get positive figures.

The gas analyzer and digital tachometer is available at all authorized service centers.


The engineers designing the vehicles may not have come through our discussion here to know how easily an engine can be tuned for mileage and performance with a mere screwdriver. Other possible reason is that they are not outputs of our private management engineering colleges where 45% marks is more than enough to get admission for any course from AE to PE and at least 8 years, instead of 4, is allowed to pass the degree examination.
Hope these links may be helpful here.
1. http://www.automotiveu.com/tuningperformance.htm
2. http://www.automotiveu.com/performancetuningpt2.htm
3.http://www.enginebuildermag.com/Item/15762/carburetor_tuning_the_airfuel_equation.aspx

A little OT.
But you'd be surprised to know that a K&N representative once explained to me that, the only alteration needed to be done after plonking in a RC1060/RC1100 was to tune the carb with a screwdriver.
And this was one of their official rep's not the retail outlet guys.

How are you sure that I will be surprised while hearing this moronic nonsense of that representative?

From where did that representative take his engineering degree and who told you that K&N “air filter” is filtering air?

Cool bro, wasnt supporting the theory that everything can be done with the help of a screwdriver. Was pointing out the ignorance which is commonly prevails, if a rep of a reputed company says like this then you can imagine the plight of the common people sitting at the place where you do polution checks. They retune carb without any detailed knowledge on the same.

Carburetors have adjustment screws , how else to manipulate those other than using screwdrivers ? I am sure that even the factory uses screwdrivers to accomplish this . Yes the factory doesn't have time to tune each carb individually by riding each vehicle , they have a test bench where carbs are tuned optimally before fitting . I say "optimally" because carburetors don't have one single exact precision tune that is the best , they have a range of good tune, some which may be better for some riding conditions or other(varies for example with altitude) . ASCs use handheld rpm meter only other than a screwdriver . Gas emission testing is not done for tuning the carb generally , unless a PUC is also asked for . Yes , I agree with you that I myself am not confident or have enough experience to go tuning carburetors without an accurate rpm-meter at least, but I have seen many mechanics have this experience and are able to do it correctly without rpm-meters too . If someone is able to reach the same position of two screws without using an rpm-meter (or gas analysis) that I can reach only with such equipment , I have no objection to it . Carburetors are really not more complicated than that .

Carb Vs Screw driver is pretty old to this thread and i thought we are settled on this topic long time back; seems some one sctatching the old injury with the new screw driver.

For me a knowledgeable person tuning with screw driver for the required purpose doesn't harm; but end users (owner cum drivers) playing with screw driver will certainly harm the engine

example service engineer or subject mater expert (a rare species called good local mechanic) tuning carb makes some sense; but end users (owner cum drivers) playing with the screwdriver and carb when ever mileage goes down is really Bad

Sorry , I wasn't aware of previous debate and strong feelings about this .
Yah , I that's what I do now, let the head-mechanic at my ASC do it .. he uses a handheld meter & screwdriver for this .
But I also don't think it would be difficult for an end-user to learn up either and what other way to learn swimming unless you get into the water ? Yes, going at it without knowing what you are doing can cause some trouble , but isn't that with everything ?
I am waiting to learn it well too (can come in handy some day while riding lonely, no? ), and trying to get myself such a meter . I have already made a few attempts at it , reaching at very good tune a few times too .. not so good at all throttle positions on others . So then I went to the ASC and the guy there did it for me for free , big deal ! I don't think that you can cause any damage to the engine trying to tune the carburetor , unless you have no clue to what you are doing at all . At most , my bike didn't run as well as I'd wished it to until I got it corrected . That's it .
But yes , tinkering with the carb just because your fuel-mileage suddenly went down would be a pretty dumb thing to do .

Was not telling to any particular person either you or punarvasu or whomesoever

was said that as i have seen in many threads where some new members with out reading the sentences properly out of overenthusiastic screwed up their bike with a screw driver then blaming company ASS blah blah blah

Tht's alryty , I'm curious .. what is the make and model of the GS150R carb ?

Some one said it says padmini on carb

but on many GS150R its mikuni BS26 i believe