How to do carb tuning

[Joe_Boxer]

Hi guys & sorry to bring up this topic again..

 

A newbie here. Anw, by reading about how to do carb tuning, i got a ques to ask. Im riding a Krr150 and has done some mod on the block, piston and etc... So my ques is, i jz bought a new racing carb size 32mm.. So before changing the main jets and all, wat do i do 1st?

-Tighten or loosen the fuel mixture 1st?

-Idling screw (tat control the throttle valve heights) shld i tighten or loosen it 1st?

Cuz i was thinking, b4 selecting the best main jet and pilot jet, do we need to tighten or loosen all the screws 1st b4 proceeding to the next steps?

[adesmond2]

Hi guys & sorry to bring up this topic again..

 

A newbie here. Anw, by reading about how to do carb tuning, i got a ques to ask. Im riding a Krr150 and has done some mod on the block, piston and etc... So my ques is, i jz bought a new racing carb size 32mm.. So before changing the main jets and all, wat do i do 1st?

-Tighten or loosen the fuel mixture 1st?

-Idling screw (tat control the throttle valve heights) shld i tighten or loosen it 1st?

Cuz i was thinking, b4 selecting the best main jet and pilot jet, do we need to tighten or loosen all the screws 1st b4 proceeding to the next steps?

 

*based on my small small experience (Pros, pls correct me if I'm wrong) Only know a little bit on tuning..

-Don't touch your idling screw

-Tighten your air screw den open to the "best" sound, usually around 2.5~3 turns (1 full turn=2 turns)

 

Jets has to be selected before you can tune.. and if you don't get the best performance, purchase another set of jets den retune again..

 

Just my 2 cent of comment..

Edited November 23, 2010 by adesmond2

[Joe_Boxer]

*based on my small small experience (Pros, pls correct me if I'm wrong) Only know a little bit on tuning..

-Don't touch your idling screw

-Tighten your air screw den open to the "best" sound, usually around 2.5~3 turns (1 full turn=2 turns)

 

Jets has to be selected before you can tune.. and if you don't get the best performance, purchase another set of jets den retune again..

 

Just my 2 cent of comment..

 

Meaning is tat, i dun adjust anything Bt to select the best main jet 1st. Ok, i get it now.. Sorry again, im abit confuse for the pilot jet part. Tried reading the info given bt seriously im lost ! Lol !! Aftr selected best main jet, how to knw if my pilots are too big or small? I gues, the needles are fine bt now comes the pilot jet, headache ! Lol !

[Pandoras Kitten 3]

Meaning is tat, i dun adjust anything Bt to select the best main jet 1st. Ok, i get it now.. Sorry again, im abit confuse for the pilot jet part. Tried reading the info given bt seriously im lost ! Lol !! Aftr selected best main jet, how to knw if my pilots are too big or small? I gues, the needles are fine bt now comes the pilot jet, headache ! Lol !

 

You might want to read up on how various settings (pilot, slide, etc) affects fuel delivery in each throttle position. If you're still interested in DIYing I can whip up a reading list for you to go through before your next practical attempt.

[adesmond2]

Meaning is tat, i dun adjust anything Bt to select the best main jet 1st. Ok, i get it now.. Sorry again, im abit confuse for the pilot jet part. Tried reading the info given bt seriously im lost ! Lol !! Aftr selected best main jet, how to knw if my pilots are too big or small? I gues, the needles are fine bt now comes the pilot jet, headache ! Lol !

 

you can look for him "Pandora's Kitten", he's a pro..

 

You might want to read up on how various settings (pilot' date=' slide, etc) affects fuel delivery in each throttle position. If you're still interested in DIYing I can whip up a reading list for you to go through before your next practical attempt.[/quote']

[BlkeIover]

good!!!!!!!!!!!!!!!!!!1

[Joe_Boxer]

You might want to read up on how various settings (pilot' date=' slide, etc) affects fuel delivery in each throttle position. If you're still interested in DIYing I can whip up a reading list for you to go through before your next practical attempt.[/quote']

 

Yup, interested.. Any link?

[crazydj]

I wanna ask ah, how come my bike after i change carb, i must open throttle before i electric or kick start my bike? I have to open the throttle a little bit when starting my bike.

 

Secondly, now my exhaust smells of carbon. Like when you smell those old card or modded cars with aftermarket exhaust. Fuel efficiency also goes down.

 

Is my carb setting too rich?

[crazydj]

I wanna ask ah, how come my bike after i change carb, i must open throttle before i electric or kick start my bike? I have to open the throttle a little bit when starting my bike.

 

Secondly, now my exhaust smells of carbon. Like when you smell those old cars or modded cars with aftermarket exhaust. Fuel efficiency also goes down.

 

Is my carb setting too rich?

Edited January 17, 2011 by crazydj

[Joe_Boxer]

Sorry, another prob here..

I jz notice tat wenever i start to warm up my bike before goink off, i notice tat the temp is heating up den usual. Is this becoz my main jet too big or air mixture probs? Bt wenever i wanna move off, my bike die. Wats the cause of this?

[MiddleAgedBiker]

Hi guys & sorry to bring up this topic again..

 

A newbie here. Anw, by reading about how to do carb tuning, i got a ques to ask. Im riding a Krr150 and has done some mod on the block, piston and etc... So my ques is, i jz bought a new racing carb size 32mm.. So before changing the main jets and all, wat do i do 1st?

-Tighten or loosen the fuel mixture 1st?

-Idling screw (tat control the throttle valve heights) shld i tighten or loosen it 1st?

Cuz i was thinking, b4 selecting the best main jet and pilot jet, do we need to tighten or loosen all the screws 1st b4 proceeding to the next steps?

 

Before diving in to tune the carbs, you first need to understand what each circuit in the carb does, and which screws control which circuit. Then you need to know what kind of carb is on your bike, CV or slide? When you read instructionals on the web, you must also know, what carbs are they meant for, CV or slide?

 

You also need an understanding of what circuits come into play at what throttle openings, you need this to do proper troubleshooting.

 

E.g. idle mixture ciruit controls 0 - 1/4 throttle opening, pilot jet roughly the same, needle profile perhaps 1/4-3/4 opening, main jet 3/4 - WOT, etc.

 

And most importantly, you must record the factory setting (or at least the setting on the bike when everything ran properly) before you fiddle with anything.

 

E.g. how many turns out was the fuel-mixture screw, originally?

 

Now to answer your question, assuming your bike has a CV carb, you'll need an accurate tach with graduations down to 50rpms to do this correctly. You need to hook this tach up to your bike. If you don't have this tach, try to do it by ear.

 

Set the idling screw so your bike idles at what your factory manual recommends. Most bikes are set at around 1,000rpms. Turn the bike off, then carefully turn the idle mixture screw all the way in (clockwise) till it seats and will turn no more. Count the number of turns and write it down. Most carbs come from the factory 1.5 turns out. You'll need a stubby flathead screwdriver, plus heat-resistant gloves to do this properly, or you might get burnt.

 

Unscrew the mixture screw back out to the original setting, let's assume it's 1.5 turns out. Now start the bike. Write down the RPM registering on your tach. Next slowly turn the screw in, 1/4 turns at a time (record this somewhere, you will forget) until your RPMs start to drop off about 50rpms. Record the number of turns you've turned it in.

 

Now turn it back out to the original setting (1.5 turns out). Now do the same thing as before, but turn the screw out, until the RPM drops 50RPM. Then record the number of turns out from factory setting, and write this down.

 

The correct setting will be the two extreme settings divided by two. E.g. if RPMs dropped at 1/2 turns out, and 2-1/2 turns out, (0.5 + 2.5) / 2 = 1.5 turns out. This would be your ideal fuel mixture setting.

 

If you don't have an accurate tach and don't want to buy one, you can try listening for when the idling speed drop happens. However, from personal experience, it's very hard to catch this by ear, because the change is so slight and it happens so progressively.

 

This takes time, and it will heat your engine up, so you need some kind of fan or something to blow your radiators when you're doing this.

 

Additionally, if you've not done any modifications to your bike (exhaust + air cleaner, engine porting, etc), just set the thing to the factory recommended setting. Honestly, the potential to muck this up is far greater than any kind of practical improvements you're going to feel.

[xXxRatedxXx]

Before diving in to tune the carbs, you first need to understand what each circuit in the carb does, and which screws control which circuit. Then you need to know what kind of carb is on your bike, CV or slide? When you read instructionals on the web, you must also know, what carbs are they meant for, CV or slide?

 

You also need an understanding of what circuits come into play at what throttle openings, you need this to do proper troubleshooting.

 

E.g. idle mixture ciruit controls 0 - 1/4 throttle opening, pilot jet roughly the same, needle profile perhaps 1/4-3/4 opening, main jet 3/4 - WOT, etc.

 

And most importantly, you must record the factory setting (or at least the setting on the bike when everything ran properly) before you fiddle with anything.

 

E.g. how many turns out was the fuel-mixture screw, originally?

 

Now to answer your question, assuming your bike has a CV carb, you'll need an accurate tach with graduations down to 50rpms to do this correctly. You need to hook this tach up to your bike. If you don't have this tach, try to do it by ear.

 

Set the idling screw so your bike idles at what your factory manual recommends. Most bikes are set at around 1,000rpms. Turn the bike off, then carefully turn the idle mixture screw all the way in (clockwise) till it seats and will turn no more. Count the number of turns and write it down. Most carbs come from the factory 1.5 turns out. You'll need a stubby flathead screwdriver, plus heat-resistant gloves to do this properly, or you might get burnt.

 

Unscrew the mixture screw back out to the original setting, let's assume it's 1.5 turns out. Now start the bike. Write down the RPM registering on your tach. Next slowly turn the screw in, 1/4 turns at a time (record this somewhere, you will forget) until your RPMs start to drop off about 50rpms. Record the number of turns you've turned it in.

 

Now turn it back out to the original setting (1.5 turns out). Now do the same thing as before, but turn the screw out, until the RPM drops 50RPM. Then record the number of turns out from factory setting, and write this down.

 

The correct setting will be the two extreme settings divided by two. E.g. if RPMs dropped at 1/2 turns out, and 2-1/2 turns out, (0.5 + 2.5) / 2 = 1.5 turns out. This would be your ideal fuel mixture setting.

 

If you don't have an accurate tach and don't want to buy one, you can try listening for when the idling speed drop happens. However, from personal experience, it's very hard to catch this by ear, because the change is so slight and it happens so progressively.

 

This takes time, and it will heat your engine up, so you need some kind of fan or something to blow your radiators when you're doing this.

 

Additionally, if you've not done any modifications to your bike (exhaust + air cleaner, engine porting, etc), just set the thing to the factory recommended setting. Honestly, the potential to muck this up is far greater than any kind of practical improvements you're going to feel.

 

Very informative.... but by this you mean if not really serious issue then don't fool with it? haha....

[bobiee]

nice tips bro !

[edwinwu91]

i am looking for fuel jet, bubbles and mirrors for my kawasaki kr. my fuel jet is those racing type, FC too high but good for racing. pm me if you have any of these. If either one of you guys will to do tuning carb and DIY service, pm me too. I am interested cause i am a noob too. remmeber to ask a pro along. if not later we open up everything dunno how to put back.

[meme56]

Very informative thread, Ty!

[georgekoh]

Any pros out there willing to provide pictures with step by step procedures?

[ColdWarCrisis]

Any of u know a reliable shop that do this carb tuning cause my fc is very bad aft a malaysian mech "tuned" it

[wasiyamo]

wads e effect for tuning carb ?? faster speed ? o_0 . pls enlight

 

If the engine pulls better when fully Dafont Showbox Adam4adam warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k. If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set. Do not pay too much attention to the lowend richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle

Edited September 23, 2019 by wasiyamo

[adesmond2]

If the engine pulls better when fully Dafont Showbox Adam4adam warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k. If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set. Do not pay too much attention to the lowend richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle

 

Bro.. your reply is 15 years late.. hahaha.. I think the person either become pro or change bike liao..

 

The post is from 2004..

[kaiq]

It's not a real person replying - it's a bot that picks any related thread and post some half-related replies. Very common here nowadays.

[adesmond2]

It's not a real person replying - it's a bot that picks any related thread and post some half-related replies. Very common here nowadays.

 

ops.. bots reply so smart ah? still know about RPM 5k-7k?

 

AI.. jia lat liao la..