How to fine-tune your jetting: Difference between revisions

Line 1:

[[Category:Intake]]

'''Carb adjustment~~'''~~

=Before you start=

Jetting is 100% bike specific.

Each bike will need something slightly different, even if they're in the Exact same location. And we all know that the majority of us aren't really close to many others.... location REALLY means major differences in what works best.

The best solution is taking the bike to a professional with a Dyno and an EGA (electronic gas analyzer, sometimes called a "Sniffer" or "4 gas analyzer") to see what kind of exhaust the bike is putting out at the different RPMs while under appropriate load. The next best solution is to dive head and heels into the massive amount of jetting information that's been published. There are dozens of different books dedicated to the subject. You'll have to read, then apply the information learned so you can feel what lean and rich are like. There's absolutely no way to impart that knowledge in the space of the FAQ.

=Carb adjustment=

'''DO NOT''' begin tearing the bike apart until you have read this ENTIRE document. You need to understand the fine tuning process before you start pulling main jets out of a hat!

~~'''~~Step 1~~'''~~: [[How do I remove the carbs to work on them?|Remove the carbs]]

==Step 1: [[How do I remove the carbs to work on them?|Remove the carbs]]==

~~'''~~Step 2~~'''~~: New main jets

==Step 2: New main jets==

Remove the float bowls (4 screws.) Unscrew the main jet: the main jet screws into a nut. Hold this with pliers and turn the jet out with a flathead screwdriver. The jet will be in there TIGHT. Make absolutely sure you are using a flat head that fits properly or you will strip the jet.

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Line 22:

Reassemble.

~~'''~~Step 3~~'''~~: Raise needles

==Step 3: Raise needles==

Remove the black covers on the top of the carbs. The screws have different lengths, so keep track of which one goes where. The plastic vacuum pistons are held under pressure by a spring, so be careful when removing the top.

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The big key to this is to not have sticky bolts... If they are stuck, you'll need to pull the carbs so you can put them in a bench vise and hit them with an impact driver.

~~'''~~Step 4~~'''~~: [[Removing idle mixture screw plugs|Adjust mixture screws]]

==Step 4: [[Removing idle mixture screw plugs|Adjust mixture screws]]==

Note: Turning the screws IN decreases the amount of gas at idle. Turning the screws OUT increases the amount of gas at idle.

~~'''~~Step 5~~'''~~: [[How do I remove the carbs to work on them?|Attach carbs to bike]]

==Step 5: [[How do I remove the carbs to work on them?|Attach carbs to bike]]==

~~'''~~Conclusions~~'''~~

==Conclusions==

It is recommended, but not necessary, that you buy [http://www.knfilters.com/search/product.aspx?Prod=RC-1822 K&N] or [http://www.unifilter.com/whoisuni.html UNI] pod filters if you are going to put an aftermarket exhaust on your bike. They make things so much easier. Do this BEFORE buying an exhaust. New filters and exhaust are not likely to net you more than a horsepower or two on such a small engine, but pod filters make carb maintenance easier.

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Line 53:

*They may contribute to [[What is carburetor ice?|Carb icing]].

=Carb Tuning=

~~'''~~Carb Tuning~~'''~~

You have three areas to tune: idle, midrange, and upper. You start at the main jet and work your way down to the mixture screws.

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'''NOTE''': DO NOT simply survey for jetting settings and expect to drop in parts. That will not work. You CANNOT properly jet from arbitrary settings. You MUST start from stock, addressing each area one at a time. Hence, this will take the better part of a day/couple of days if you want it done right.

Step 1: Find the proper main jet.

==Step 1: Find the proper main jet.==

Start from the stock jet and needle height, and increase the main jet size by ONE SIZE at a time, until you feel the upper too rich. Then back up to the previous size. Please note that the amount of gas passed by the main jet increases exponentially with main jet size, as the circumference of a circle increases exponentially with diameter! What that means is that the difference between jet sizes is not equal.

Example:

'''Example:'''

~Start from stock.

Line 78:

Line 85:

RICH = Bogging. Runs better when bike is cold. Black plugs.

Step 2: Find the proper needle height.

==Step 2: Find the proper needle height.==

Start from tuned jet and stock needle height, and repeat the same process used for the main jet.

Start from tuned jet and stock needle height, and repeat the same process used for the main jet. If it runs better with more washers, when you get to about 4, go up a size on the main jets and start with stock needle height again. Continue to add/remove washers until it runs correctly.

Symptoms:

Line 88:

Line 95:

RICH = Bogging. Runs better when bike is cold. Black plugs.

Step 3: Find the proper idle mixture.

==Step 3: Find the proper idle mixture.==

Find a short (2" or less) screwdriver or driver bit and adjust the mixture screws with the carb on the bike and the bike running. Turning the screws IN decreases the amount of gas. Turning the screws OUT increases the amount of gas.

Line 98:

Line 105:

RICH = Blipping throttle causes the RPMs to rise, drop down below the idle speed setting, and the rise back up.

~~'''~~Conclusions~~'''~~

==Conclusions==

Ideally, you would follow these steps, examining the plugs after each step. However, in the absence of a dyno machine, it's not always possible to find a place where you can, for example, do several full throttle runs and immediately shut the bike down and examine the plugs, while doing carb adjustments on the spot!

Line 104:

Line 111:

It is advisable though, to monitor overall plug conditions after the jetting process. "Feeling" the bike will get you close, plug color can help you nail it. See the links on the [[Changing the spark plugs & brands to avoid|Spark Plug page]] for information on plug color.

~~'''And remember:'''~~

=If you're getting a jet kit=

~~Jetting is 100% bike specific.~~

Each bike will need something slightly different, even if they're in the Exact same location. And we all know that the majority of us aren't really close to many others.... location REALLY means major differences in what works best.

The best solution is taking the bike to a professional with a Dyno and an EGA (electronic gas analyzer, sometimes called a "Sniffer" or "4 gas analyzer") to see what kind of exhaust the bike is putting out at the different RPMs while under appropriate load. The next best solution is to dive head and heels into the massive amount of jetting information that's been published. There are dozens of different books dedicated to the subject. You'll have to read, then apply the information learned so you can feel what lean and rich are like. There's absolutely no way to impart that knowledge in the space of the FAQ.

===If you're getting a jet kit===

[[How do I install a jet kit?|Factory Pro]] is the recommended jet kit for the Ninja 250. If you get one of theirs, it only makes sense to follow their [http://www.factorypro.com/tech/carbtun.html tuning guidelines]. Obviously, follow the link to high rpm engines.

@@ Line 1: / Line 1: @@
 [[Category:Intake]]
-'''Carb adjustment'''
+=Before you start=
+Jetting is 100% bike specific.
+Each bike will need something slightly different, even if they're in the Exact same location. And we all know that the majority of us aren't really close to many others.... location REALLY means major differences in what works best.
+The best solution is taking the bike to a professional with a Dyno and an EGA (electronic gas analyzer, sometimes called a "Sniffer" or "4 gas analyzer") to see what kind of exhaust the bike is putting out at the different RPMs while under appropriate load. The next best solution is to dive head and heels into the massive amount of jetting information that's been published. There are dozens of different books dedicated to the subject. You'll have to read, then apply the information learned so you can feel what lean and rich are like. There's absolutely no way to impart that knowledge in the space of the FAQ.
+=Carb adjustment=
 '''DO NOT''' begin tearing the bike apart until you have read this ENTIRE document. You need to understand the fine tuning process before you start pulling main jets out of a hat!
-'''Step 1''': [[How do I remove the carbs to work on them?|Remove the carbs]]
+==Step 1: [[How do I remove the carbs to work on them?|Remove the carbs]]==
-'''Step 2''': New main jets
+==Step 2: New main jets==
 Remove the float bowls (4 screws.) Unscrew the main jet: the main jet screws into a nut. Hold this with pliers and turn the jet out with a flathead screwdriver. The jet will be in there TIGHT. Make absolutely sure you are using a flat head that fits properly or you will strip the jet.
@@ Line 14: / Line 22: @@
 Reassemble.
-'''Step 3''': Raise needles
+==Step 3: Raise needles==
 Remove the black covers on the top of the carbs. The screws have different lengths, so keep track of which one goes where. The plastic vacuum pistons are held under pressure by a spring, so be careful when removing the top.
@@ Line 28: / Line 36: @@
 The big key to this is to not have sticky bolts... If they are stuck, you'll need to pull the carbs so you can put them in a bench vise and hit them with an impact driver.
-'''Step 4''': [[Removing idle mixture screw plugs|Adjust mixture screws]]
+==Step 4: [[Removing idle mixture screw plugs|Adjust mixture screws]]==
 Note: Turning the screws IN decreases the amount of gas at idle. Turning the screws OUT  increases the amount of gas at idle.
-'''Step 5''': [[How do I remove the carbs to work on them?|Attach carbs to bike]]
+==Step 5: [[How do I remove the carbs to work on them?|Attach carbs to bike]]==
-'''Conclusions'''
+==Conclusions==
 It is recommended, but not necessary, that you buy [http://www.knfilters.com/search/product.aspx?Prod=RC-1822 K&N] or [http://www.unifilter.com/whoisuni.html UNI] pod filters if you are going to put an aftermarket exhaust on your bike. They make things so much easier. Do this BEFORE buying an exhaust. New filters and exhaust are not likely to net you more than a horsepower or two on such a small engine, but pod filters make carb maintenance easier.
@@ Line 45: / Line 53: @@
 *They may contribute to [[What is carburetor ice?|Carb icing]].
+=Carb Tuning=
-'''Carb Tuning'''
 You have three areas to tune: idle, midrange, and upper. You start at the main jet and work your way down to the mixture screws.
@@ Line 54: / Line 61: @@
 '''NOTE''': DO NOT simply survey for jetting settings and expect to drop in parts. That will not work. You CANNOT properly jet from arbitrary settings. You MUST start from stock, addressing each area one at a time. Hence, this will take the better part of a day/couple of days if you want it done right.
-Step 1: Find the proper main jet.
+==Step 1: Find the proper main jet.==
 Start from the stock jet and needle height, and increase the main jet size by ONE SIZE at a time, until you feel the upper too rich. Then back up to the previous size. Please note that the amount of gas passed by the main jet increases exponentially with main jet size, as the circumference of a circle increases exponentially with diameter! What that means is that the difference between jet sizes is not equal.
-Example:
+'''Example:'''
 ~Start from stock.
@@ Line 78: / Line 85: @@
 RICH = Bogging. Runs better when bike is cold. Black plugs.
-Step 2: Find the proper needle height.
+==Step 2: Find the proper needle height.==
-Start from tuned jet and stock needle height, and repeat the same process used for the main jet.
+Start from tuned jet and stock needle height, and repeat the same process used for the main jet. If it runs better with more washers, when you get to about 4, go up a size on the main jets and start with stock needle height again. Continue to add/remove washers until it runs correctly.
 Symptoms:
@@ Line 88: / Line 95: @@
 RICH = Bogging. Runs better when bike is cold. Black plugs.
-Step 3: Find the proper idle mixture.
+==Step 3: Find the proper idle mixture.==
 Find a short (2" or less) screwdriver or driver bit and adjust the mixture screws with the carb on the bike and the bike running. Turning the screws IN decreases the amount of gas. Turning the screws OUT increases the amount of gas.
@@ Line 98: / Line 105: @@
 RICH = Blipping throttle causes the RPMs to rise, drop down below the idle speed setting, and the rise back up.
-'''Conclusions'''
+==Conclusions==
 Ideally, you would follow these steps, examining the plugs after each step. However, in the absence of a dyno machine, it's not always possible to find a place where you can, for example, do several full throttle runs and immediately shut the bike down and examine the plugs, while doing carb adjustments on the spot!
@@ Line 104: / Line 111: @@
 It is advisable though, to monitor overall plug conditions after the jetting process. "Feeling" the bike will get you close, plug color can help you nail it. See the links on the [[Changing the spark plugs & brands to avoid|Spark Plug page]] for information on plug color.
-'''And remember:'''
+=If you're getting a jet kit=
-Jetting is 100% bike specific.
-Each bike will need something slightly different, even if they're in the Exact same location. And we all know that the majority of us aren't really close to many others.... location REALLY means major differences in what works best.
-The best solution is taking the bike to a professional with a Dyno and an EGA (electronic gas analyzer, sometimes called a "Sniffer" or "4 gas analyzer") to see what kind of exhaust the bike is putting out at the different RPMs while under appropriate load. The next best solution is to dive head and heels into the massive amount of jetting information that's been published. There are dozens of different books dedicated to the subject. You'll have to read, then apply the information learned so you can feel what lean and rich are like. There's absolutely no way to impart that knowledge in the space of the FAQ.
-===If you're getting a jet kit===
 [[How do I install a jet kit?|Factory Pro]] is the recommended jet kit for the Ninja 250. If you get one of theirs, it only makes sense to follow their [http://www.factorypro.com/tech/carbtun.html tuning guidelines]. Obviously, follow the link to high rpm engines.