Carburetor Thread

[abhisheklakhanpal]

i got a pulsar 180 ug2..
got it tuned at the service centre 2 days ago...
but its kind of givin me probs...
at the top gear and about 6000rpm, i feel like it is running out of fuel..der is no prob in the remaining gears....
help...

The bajaj auto guys are trained to reduce the fuel/ air settings after a service so as to give an apparent feel to the customer that the bike is smooth. Even if you ask them to adjust it on a day other than service day , they normally just try to give you a smoother feel . Hence the feeling of lower fuel flow.

Okay. You need to increase the air intake setting or the fuel intake stting (Not both though). Either is not in congruence with the other and is acting as a limiting factor . In your case i think is probably the fuel.


(PS: You should also check your fuel pipe for any blockage. CHeck at the point where the fuel reserve switch is . IF the flow is uniform then its okay . If the flow is jerky on a reasonaly filled tank(5 litres) then your fuel line may have a blockage.

Also ensure your chain is properly done. lol. ok.Something i always do.)

[abhisheklakhanpal]

ok,i have a doubt.
I want to set a richer mix for my FZ,so should i be setting the idle RPM to 3k?

Idle Rpm as high as 3k wont help . fot initial pickup increasing the idle rpm by uptp 200 will be slightly helpful For fz i think the factory idle rpm is 1300-1400 so you could try going upto 1600 max. The rest of the rich mix will depend o how well you adjust the fuel - air ratio .This means both settings are high. Idle rpm is only facilitator for very initial stage of pick up,.

[madhav krishna]

So ,
i figure most of us are still riving around carburetted bikes and at some point of time , some dumb ass mechanic will screw it up for you (like a Bajaj Auth Service for me ) , or some drastic altitude changes will leave you feeling powerless. This goes to say , that your carburettor will be out of tune .

So , while i have kinda figured the trick , i m sure none of you wanna be slaves to these headless mechanics waiting to tune a blunder for you .


A little Guide to tune you 4 stroke CV carburettor for the optimal ( Not power oriented ) air fuel mixture.

There are mainly two screws used for the tunning of a carburetor

1.Fuel screw(4 stroke) or air screw (2 stroke)
2.Idle Rpm screw

The main difference between two stroke the fuel screw is that for the fuel screw(used in pulsar etc) Clockwise tightening makes the mixture lean , and anticlockwise loosening makes the mixture rich.

For two stroke bikes using an air screw the setting is exactly opposite.



Judging the air-fuel mixture for the bike can only be done on a warmed up engine.

Warming up the engine

1.Drive for atleast 10-15minutes before trying to adjust any of the carburetor setting.
2.Especially for CV carburetors, used in the pulsar, use 1/2 throttle on an uphill for 1 minute. ( alternative )

Setting the mixture

1.Set the idle screw at 3000rpm
2.Now adjust the fuel screw for the leanest possible mix without stalling the engine.
3.Now after adjustment is made the rpm becomes constant
4.Now , adjust screw to tune within the lean range
5.Decrease idle rpm to about 1100
6.Check the throttle for a quick and crisp response. The crispiness is important
Also check for instant start


After warming and adjusting , drive for a while to check the spark plugs for the following signs
1.White Deposits : Lean Mixture
2.Black deposits : Rich mixture
3.Sandy side of chocolate brown : Ideal mixture.

Please note that the fuel mixture is always checked by driving between 1/4 th and 3/4th of the total throttle twist. This also goes to imply that the throttle body must have a uniform response to the same twist at all levels and is working perfectly.
The other , not so accurate way to check the correct mixture is the silencer or exhaust fume . Place your hand at the exhaust as you rake the engine after 1/4th of the throttle .

1.The sign of the optimal mix is that your hand feel slight warmish moisture as the throttle is increased a bit . Then check the same sign at constant throttle.
2.The very heat or temperature of the fumes at the upper limit of the power band should not feel too much to keep the hand there for about 10 seconds.


A few signs for your carburetor out of tunning
1.RPM rises fast but reduces slowly : Mixture is not optimal , usually on the leaner side.
2.Grunting sound (too much torque) : Rich mixture.
3.Engine knocking at low rpm without power : Lean
4.Not enough power , overracing at high rpm for same speed : Clutch setting req . Mix is a little lean



A Lean mixture is usally more harmful than a richer one . This is because , the engine is knocking at a higher rate for the same power . Thus the high compression damages the pistons causing holing(hole in the top center of the piston).It also jerks the entire combustion chamber which may loosen the o-rings as well as cause uneven wear.
For this reason it is necessary that you always try to keep the needle in the powerband for medium and overdrive gears, and also never try and keep the bike in the same gear for thought of better efficiency.

For those of you who think that a richer mixture is a gateway for more power, it may be noteworthy of a mention that even a richer mix is damaging and causes faster wear and tear.

Hence engine life is reduced though it will function better than a len mixed carburettor. In case performance is what you look at , Jetting of the carburettor is the right way to go. It is basically increasing the fuel pipe radius as well as the air pipe, to allow for a greater fuel flow rate. The most significant increase of jetting is felt at the top end , where the limiting fuel flow is increased, thought a difference is also felt throughout the entire RPM range.

However , once you drive a day or two , you will figure if your setting is correct or not . If the mixture is the optimal one then just a single anticlockwise turn ( richer) or maybe two will give you a reasonable boost in the power , though naturally you are sacrificing the Fuel effiency , although it wont matter much . But , repeat , test the optimal setting for atleast two days , before switching to the optimally rich setting . Coz knowing what is right is the only way to know , know what is beyond right.





Towards biking Independence......

Cheers!

dude can the same method b used to tune the carburetter of yamaha gladiator?? please post the pictures of the 2 screws as identifying them is hard & how 2 check if the fuel mixture is lean or rich using an much easier method other then the one u told??

[jonahmano]

There are two more versions....

And Here are the other two versions, bit similar but I did understand you meant only by reading the other two which I am pasting below.........

Version 1Troubleshooting
Version 2

[Legend Racer]

And Here are the other two versions, bit similar but I did understand you meant only by reading the other two which I am pasting below.........

Version 1Troubleshooting
Version 2

whats the difference if i set it at 3000rpm or 5000rpm, and then start doing the tuning?

[Legend Racer]

plz replyyyyyyyyyyyyyyyyyyyy

whats the difference if i set it at 3000rpm or 5000rpm, and then start doing the tuning?

whats the difference if i set it at 3000rpm or 5000rpm, and then start doing the tuning?

[road_ripper]

And Here are the other two versions, bit similar but I did understand you meant only by reading the other two which I am pasting below.........

Version 1Troubleshooting
Version 2

Please mention the link and give coutesy to the writer after the copy paste job is done...
The source of this review is given below
GENERAL ADVICE ON BIKES Review, GENERAL ADVICE ON BIKES Price, GENERAL ADVICE ON BIKES Mileage, Tuning your carburettor for optimal performance & - MouthShut.com

[road_ripper]

whats the difference if i set it at 3000rpm or 5000rpm, and then start doing the tuning?

I keep it at 4000 rpm and tune the bike.. the result is good of both the worlds, I get mileage of 43-45 with superb acceleration on my 180 ug3.
When i had tuned the bike keeping at 3000 rpm, the mileage was 45+ but pickup was not that brisk, So I guess lesser rpm will tune it for mileage and higher rpm will tune your bike for power...

[Legend Racer]

confused

I keep it at 4000 rpm and tune the bike.. the result is good of both the worlds, I get mileage of 43-45 with superb acceleration on my 180 ug3.
When i had tuned the bike keeping at 3000 rpm, the mileage was 45+ but pickup was not that brisk, So I guess lesser rpm will tune it for mileage and higher rpm will tune your bike for power...

are you sure bro?..but that work is done by A/F screw..isnt?a bit confused?could you explain?

[Yasir Qaiyum]

Hi guys!! I read this thread in morning and decided to tune by bike(pulsar150UG4).. the problem is I couldnt find any screw except the one which is in golden color... It is on the left side of carb.. which screw is that? And where is the other screw (air screw or fuel screw)....PLEASE HELP...

[Legend Racer]

ok

Hi guys!! I read this thread in morning and decided to tune by bike(pulsar150UG4).. the problem is I couldnt find any screw except the one which is in golden color... It is on the left side of carb.. which screw is that? And where is the other screw (air screw or fuel screw)....PLEASE HELP...

easy dude..u can find with patience...sit on the left side.u found out the idle screw..nice..now just to the left of that on carb.its a small one.just note that ur screw driver meets this screw in perpendicular.i mean if u turn thz clockwise thz goes inside the carb and vice versa..hope thz wud b easy to find.take care u should not fiddle with thz screw simply..take care.its properly instructed in thread.i did mine P150 UG2 @ 3000 rpm..i did for my frd @ 4000rpm..thr is difference in pick up.i ve posted my doubt in this.i mean till wat rpm u can get utmost acceleration jst by thz tuning.

[jonahmano]

Hi guys!! I read this thread in morning and decided to tune by bike(pulsar150UG4).. the problem is I couldnt find any screw except the one which is in golden color... It is on the left side of carb.. which screw is that? And where is the other screw (air screw or fuel screw)....PLEASE HELP...

Yaseer pls read the 3 versions carefully one which was posted by abhiskeh and other two posted by me.....o.k.

YOur's is Pulsar 150 4 stroke and the one which you found in goldern color is the fuel screw, so you got the fuel scerw

Now you know what is the idle screw, idle screw is that which is connected to accelerator cable just turn the accelerator cable and look near the carburettor you can find some movement that is idle screw.

Now read the three version carefully two or three times and you will get some idea

Better you take help of your friend


Good Luck

[jonahmano]

Please mention the link and give coutesy to the writer after the copy paste job is done...
The source of this review is given below
GENERAL ADVICE ON BIKES Review, GENERAL ADVICE ON BIKES Price, GENERAL ADVICE ON BIKES Mileage, Tuning your carburettor for optimal performance & - MouthShut.com

I haven't started this thread and I saw the first person didn't give any link so I too thought I didn't need to give a link.

I do wonder even the linked writer must have copy/pasted from somewhere else.

Who knows who is the writer, we need our job to be get done

And I don't want any applause from anybody here.

I want to help as I am getting help from this forum (Xbhp) that's all

I hope you understand me

[Yasir Qaiyum]

easy dude..u can find with patience...sit on the left side.u found out the idle screw..nice..now just to the left of that on carb.its a small one.just note that ur screw driver meets this screw in perpendicular.i mean if u turn thz clockwise thz goes inside the carb and vice versa..hope thz wud b easy to find.take care u should not fiddle with thz screw simply..take care.its properly instructed in thread.i did mine P150 UG2 @ 3000 rpm..i did for my frd @ 4000rpm..thr is difference in pick up.i ve posted my doubt in this.i mean till wat rpm u can get utmost acceleration jst by thz tuning.

@legend racer & jonahmanu-- Thank You guys for clearing my doubts...

[daredemon]

So ,
i figure most of us are still riving around carburetted bikes and at some point of time , some dumb ass mechanic will screw it up for you (like a Bajaj Auth Service for me ) , or some drastic altitude changes will leave you feeling powerless. This goes to say , that your carburettor will be out of tune .

So , while i have kinda figured the trick , i m sure none of you wanna be slaves to these headless mechanics waiting to tune a blunder for you .


A little Guide to tune you 4 stroke CV carburettor for the optimal ( Not power oriented ) air fuel mixture.

There are mainly two screws used for the tunning of a carburetor

1.Fuel screw(4 stroke) or air screw (2 stroke)
2.Idle Rpm screw

The main difference between two stroke the fuel screw is that for the fuel screw(used in pulsar etc) Clockwise tightening makes the mixture lean , and anticlockwise loosening makes the mixture rich.

For two stroke bikes using an air screw the setting is exactly opposite.



Judging the air-fuel mixture for the bike can only be done on a warmed up engine.

Warming up the engine

1.Drive for atleast 10-15minutes before trying to adjust any of the carburetor setting.
2.Especially for CV carburetors, used in the pulsar, use 1/2 throttle on an uphill for 1 minute. ( alternative )

Setting the mixture

1.Set the idle screw at 3000rpm
2.Now adjust the fuel screw for the leanest possible mix without stalling the engine.
3.Now after adjustment is made the rpm becomes constant
4.Now , adjust screw to tune within the lean range
5.Decrease idle rpm to about 1100
6.Check the throttle for a quick and crisp response. The crispiness is important
Also check for instant start


After warming and adjusting , drive for a while to check the spark plugs for the following signs
1.White Deposits : Lean Mixture
2.Black deposits : Rich mixture
3.Sandy side of chocolate brown : Ideal mixture.

Please note that the fuel mixture is always checked by driving between 1/4 th and 3/4th of the total throttle twist. This also goes to imply that the throttle body must have a uniform response to the same twist at all levels and is working perfectly.
The other , not so accurate way to check the correct mixture is the silencer or exhaust fume . Place your hand at the exhaust as you rake the engine after 1/4th of the throttle .

1.The sign of the optimal mix is that your hand feel slight warmish moisture as the throttle is increased a bit . Then check the same sign at constant throttle.
2.The very heat or temperature of the fumes at the upper limit of the power band should not feel too much to keep the hand there for about 10 seconds.


A few signs for your carburetor out of tunning
1.RPM rises fast but reduces slowly : Mixture is not optimal , usually on the leaner side.
2.Grunting sound (too much torque) : Rich mixture.
3.Engine knocking at low rpm without power : Lean
4.Not enough power , overracing at high rpm for same speed : Clutch setting req . Mix is a little lean



A Lean mixture is usally more harmful than a richer one . This is because , the engine is knocking at a higher rate for the same power . Thus the high compression damages the pistons causing holing(hole in the top center of the piston).It also jerks the entire combustion chamber which may loosen the o-rings as well as cause uneven wear.
For this reason it is necessary that you always try to keep the needle in the powerband for medium and overdrive gears, and also never try and keep the bike in the same gear for thought of better efficiency.

For those of you who think that a richer mixture is a gateway for more power, it may be noteworthy of a mention that even a richer mix is damaging and causes faster wear and tear.

Hence engine life is reduced though it will function better than a len mixed carburettor. In case performance is what you look at , Jetting of the carburettor is the right way to go. It is basically increasing the fuel pipe radius as well as the air pipe, to allow for a greater fuel flow rate. The most significant increase of jetting is felt at the top end , where the limiting fuel flow is increased, thought a difference is also felt throughout the entire RPM range.

However , once you drive a day or two , you will figure if your setting is correct or not . If the mixture is the optimal one then just a single anticlockwise turn ( richer) or maybe two will give you a reasonable boost in the power , though naturally you are sacrificing the Fuel effiency , although it wont matter much . But , repeat , test the optimal setting for atleast two days , before switching to the optimally rich setting . Coz knowing what is right is the only way to know , know what is beyond right.





Towards biking Independence......

Cheers!

Hey abhishek,
thats a good info there you have provided. It will certainly help
for a two stroker like me.