[UT]: Tuning your Motorcycle Carburettor. - Page 11 - xBhp.com : The Global Indian Biking Community

abhisheklakhanpal · 03-12-2011, 10:22 PM

Karizma Boi,

If the RPM goes up to 2k , then its normal .

I have been riding a ZMA and this is the way it is .

The ZMA carb is designed to do so .

Hope this helps.

Honda_CBF · 03-18-2011, 03:41 PM

Guys, got some product info which help carburetors to perform like fuel injection while googling..
there are many products in this site. they say;
*there will be no need to re-jetting if you upgrade your air filter & silencer to Free flow
*best balance between mileage & performance
*easy tuning
*no effect of temperature & altitude; And many more
go through this for all details:
Thunder Products - Performance carburetor and clutching for snowmobiles, motorcycles and ATVs.
Thunder Products - Performance carburetor and clutching for snowmobiles, motorcycles and ATVs.
Thunder PowerJet Performance Carburetor Clutching Snowmobile Motorcycle ATV Improved Fuel Efficiency

Lonely Rider · 05-27-2011, 05:46 PM

Hello,

I am looking pout for a BS 29 CArb for my Thunderbird. Alternatively would like to have a carb of Pulsar 180 also.

Kindly let me know if it is available.

UTKARSH STUNTY SHARMA · 09-09-2011, 11:29 PM

Quote:

Originally Posted by abhisheklakhanpal

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.

The idle rpm screw is what sets the warm engine idle rpm . The greatest significance of the idle rpm or pilot setting would crop up at the point that it affects 1/8th of the initial throttle response. After that , it’s the butterflies and other that take over . But this initial turning is critical so as to ensure a smooth pickup as well as control knocking or over racing.

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!

PLzz tell me which carburettor size i need to upjet my apache 180 ....i have a jet .its written k118s on the side walls of this jet urgent reply needed

pranjal chakraborty · 09-12-2011, 04:46 PM

Can the carb be tuned by checking the co2 level? And according to the co2 we can tune the bike to have a perfect tuning

Ramborider · 09-17-2011, 07:02 PM

my pulsar 150 classic doesnt tune by that fuel screw,i had changed pilot jet also but it dont get set properly,when release accelerator it get off and after or some time engine speed increases prematurely so what would be problem for this??
i had using 12.5 pilot jet while before that it has 17.5,as i have read from pulsar dtsi workshop manual about pilot jet size,but i have doubt is it same for old model or not

mechanic told that have to change carburettor!!please help me out any one here having pulsar 150 classic who would having idea about size of pilot jet???

rprathin · 02-15-2012, 07:55 PM

i have question for how to tune yamaha gladiator because when i completely tight the fuel screw than nothing happens.....

03-18-2011, 03:41 PM	#102 (permalink)
Honda_CBF Still learning the art of bike'in.. Join Date: Jan 2011 Location: Jamshedpur, Jharkhand Posts: 692	Carb tuning like FUEL INJECTION Guys, got some product info which help carburetors to perform like fuel injection while googling.. there are many products in this site. they say; there will be no need to re-jetting if you upgrade your air filter & silencer to Free flow best balance between mileage & performance easy tuning no effect of temperature & altitude; And many more go through this for all details: Thunder Products - Performance carburetor and clutching for snowmobiles, motorcycles and ATVs. Thunder Products - Performance carburetor and clutching for snowmobiles, motorcycles and ATVs. Thunder PowerJet Performance Carburetor Clutching Snowmobile Motorcycle ATV Improved Fuel Efficiency

05-27-2011, 05:46 PM	#103 (permalink)
Lonely Rider Senior Member Join Date: Nov 2010 Location: Bangalore Posts: 251	Hello, I am looking pout for a BS 29 CArb for my Thunderbird. Alternatively would like to have a carb of Pulsar 180 also. Kindly let me know if it is available. __________________ RE Thunderbird Since Jan 09 onwards Suzuki Zeus Jan -Dec 08 -- Sold Honda Unicorn Oct 06-Dec 08 -- Sold New edition : BSA Mach 19" 6 Speed-- Sold Schwinn Sporterra -- Up and running

09-12-2011, 04:46 PM	#105 (permalink)
pranjal chakraborty Senior Member Join Date: Mar 2011 Location: west bengal, kolkata Posts: 192	Can the carb be tuned by checking the co2 level? And according to the co2 we can tune the bike to have a perfect tuning __________________ pranjal.chakraborty8@gmail.com

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03-12-2011, 10:22 PM	#101 (permalink)
abhisheklakhanpal Junior Member Join Date: Sep 2009 Posts: 9	Karizma Boi, If the RPM goes up to 2k , then its normal . I have been riding a ZMA and this is the way it is . The ZMA carb is designed to do so . Hope this helps.

09-17-2011, 07:02 PM	#106 (permalink)
Ramborider Senior Member Join Date: Apr 2010 Location: mumbai Posts: 111	my pulsar 150 classic doesnt tune by that fuel screw,i had changed pilot jet also but it dont get set properly,when release accelerator it get off and after or some time engine speed increases prematurely so what would be problem for this?? i had using 12.5 pilot jet while before that it has 17.5,as i have read from pulsar dtsi workshop manual about pilot jet size,but i have doubt is it same for old model or not mechanic told that have to change carburettor!!please help me out any one here having pulsar 150 classic who would having idea about size of pilot jet???

02-15-2012, 07:55 PM	#107 (permalink)
rprathin life without motorcycle!!!!440 volts shock Join Date: Nov 2011 Location: Varanasi,Uttar Pradesh Posts: 96	i have question for how to tune yamaha gladiator because when i completely tight the fuel screw than nothing happens.....

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