ninjette.org - View Single Post - Shimming the Carb Needles... Is it for You?

kkim · November 11th, 2008, 08:56 PM

Shimming the needles, raising the needle jet, the washer trick… whatever you want to call it, it works for our bikes. I would rate this mod as the top DIY one should consider doing to their bike, especially if you’re a newer rider and trying to get comfortable riding it. It really does make the bike easier to ride and boosts confidence, two things any new rider can use.

While this trick has been used on the previous generation 250s, this is written specifically for the new gen (08-09) 250R. Most of the info, though, is general enough to apply to the pregens.

Many seem confused as to what it does and why one would even consider this mod. Still others worry if their bike really needs it and if they are capable of doing it. I hope this post will help clear up a lot of questions and doubts on what the symptoms are of a bike that needs it, why it’s the way it is and how to remedy it.

So, if after you read this post and want to give it a try, post your questions here and we’ll see what we can do to help.

Also, if you have done this mod and like or hate the results, please post your comments here so all that are considering doing this will have adequate feedback to decide for themselves to do this or not.

I just thought it was time to simplify the whole “shimming” decision making process.

Hope this proves useful to those wanting answers.

1- Who needs it and what will it do for my bike?

Shimming the needles will get rid of a nasty lean spot coming right off idle. If your bike stalls, hesitates, hacks or coughs when you are trying to pull off from a stop, you could use shimming. Also, if your bike needs to have the choke on to start it, when the engine is stone cold, and needs the choke on for long periods of time, you should shim.

A great DIY on how to shim is located here…
http://www.kawiforums.com/showthread.php?t=105901

2- What does this all do?

Well, if your bike is lean, shimming will make the bike seem like it has more power at the very bottom end of the rev range. (2-5K rpm) The power band seems “fatter” which leads to an easier to ride bike. If you are a beginning rider and feel the bike is hard to ride because of difficulty of getting the bike off cleanly from a stop, shimming will do wonders for your riding confidence. Start offs will seem like the bike just gets up and rides away on its own. No kidding… after shimming (if your bike is one that needs it), it will literally transform your engine power characteristics.

3- Why is my bike like this from the factory… is something wrong with it?

Kawasaki designed the 250R with fuel economy and emissions controls in mind when they selected the jetting specs. That they went with the most conservative settings to obtain good advertising results flies directly against the very market these bikes were designed for… namely, the beginning rider. The lean settings make the bike very anemic down low in the rev range which results in a very hard to control power band for the neophyte rider. Instead of having a lot of power right when you let out the clutch from a stop, the lean settings make the bike hard to negotiate cleanly from a stop. New riders have a hard enough time coordinating throttle and clutch engagement. The weak low end power just makes it that much harder for the beginning rider to pull off clean take offs, not to mention worrying about stalling the bike in the middle of an intersection.

My take on this is that the bikes are lean due to incorrect settings of the idle mixture screws at the factory. Whoever is doing them is not setting them correctly... and to make it worse, they are not setting them incorrectly consistently. This means some bikes are waaaayy too lean, some sorta lean, others just right and still others (very few) rich. How many washers you will need will depend on a couple of things. The thickness of the washers you use, the setting of your particular bike's mixture screws from the factory as well as other factors that normally affect jetting. (temp, altitude and humidity) Take all this into account and it is easy to see why there are no golden rules as to how many washers will work best for all bikes.

As is the case with all jetting work, experimentation is key to obtaining jetting perfection. I will say, while you have improved your jetting from stock by using the washers, it is far from perfect, but certainly worlds better than it was from off the showroom floor. For many, this will be all they will ever need to do to improve the jetting to make theirs an enjoyable, friendly bike.

4- Come on… at least give me a place to start!!

Okay, okay… These are some very general rule of thumb washer numbers. Expect to have to do this a couple of times if you are not satisfied with the recommendations…

1 washer for a completely stock bike.
1-2 washers for an aftermarket can or system
2-3 washers for an aftermarket system or can with the snorkel removed

5- Some caveats before deciding you should do this…

Not all people who have shimmed their bikes have met with success. There have been a few that actually installed the washers and the bike ran like crap. They ended up taking the washers back out and their bikes run fine without any washers to this day. Remember step #1? Their bikes never stalled from stops and in fact needed little or no choke at start up. These bikes are the few that were set right or a bit rich from the factory. You need to determine if the situations in #1 describe your bike. If it does, it’s a safe bet shimming will improve your bike.

If you have never worked on a bike before and would like to do this mod, read the DIY link I posted. Read it (the entire thread!) and understand it before you start tearing your bike apart. Have all the suggested tools available, especially the long #2 Phillips screwdriver. It does take some degree of mechanical skill to accomplish this task and some of the parts you will be dealing with are quite delicate. Just be clean and orderly when you work and you should do fine. Do one carb at a time as you don’t want to mix parts up between the left and right carb as some parts are different between the two.

Set aside some time to do this. If it’s your first time tearing the bike apart, plan on 4 hours. Personally, I usually allow double the time on any new project I work on, so for this I would put aside 8 hours just in case something should go wrong.

If there are any questions, please post them in this thread and the members of the board who have done this before will be more than happy to answer your questions and/or sooth your fears.

November 11th, 2008, 08:56 PM	#1
kkim Join Date: Nov 2008 Posts: Too much.	Shimming the Carb Needles... Is it for You? Shimming the needles, raising the needle jet, the washer trick… whatever you want to call it, it works for our bikes. I would rate this mod as the top DIY one should consider doing to their bike, especially if you’re a newer rider and trying to get comfortable riding it. It really does make the bike easier to ride and boosts confidence, two things any new rider can use. While this trick has been used on the previous generation 250s, this is written specifically for the new gen (08-09) 250R. Most of the info, though, is general enough to apply to the pregens. Many seem confused as to what it does and why one would even consider this mod. Still others worry if their bike really needs it and if they are capable of doing it. I hope this post will help clear up a lot of questions and doubts on what the symptoms are of a bike that needs it, why it’s the way it is and how to remedy it. So, if after you read this post and want to give it a try, post your questions here and we’ll see what we can do to help. Also, if you have done this mod and like or hate the results, please post your comments here so all that are considering doing this will have adequate feedback to decide for themselves to do this or not. I just thought it was time to simplify the whole “shimming” decision making process. Hope this proves useful to those wanting answers. *1- Who needs it and what will it do for my bike?* Shimming the needles will get rid of a nasty lean spot coming right off idle. If your bike stalls, hesitates, hacks or coughs when you are trying to pull off from a stop, you could use shimming. Also, if your bike needs to have the choke on to start it, when the engine is stone cold, and needs the choke on for long periods of time, you should shim. A great DIY on how to shim is located here… http://www.kawiforums.com/showthread.php?t=105901 *2- What does this all do?* Well, if your bike is lean, shimming will make the bike seem like it has more power at the very bottom end of the rev range. (2-5K rpm) The power band seems “fatter” which leads to an easier to ride bike. If you are a beginning rider and feel the bike is hard to ride because of difficulty of getting the bike off cleanly from a stop, shimming will do wonders for your riding confidence. Start offs will seem like the bike just gets up and rides away on its own. No kidding… after shimming (if your bike is one that needs it), it will literally transform your engine power characteristics. *3- Why is my bike like this from the factory… is something wrong with it?* Kawasaki designed the 250R with fuel economy and emissions controls in mind when they selected the jetting specs. That they went with the most conservative settings to obtain good advertising results flies directly against the very market these bikes were designed for… namely, the beginning rider. The lean settings make the bike very anemic down low in the rev range which results in a very hard to control power band for the neophyte rider. Instead of having a lot of power right when you let out the clutch from a stop, the lean settings make the bike hard to negotiate cleanly from a stop. New riders have a hard enough time coordinating throttle and clutch engagement. The weak low end power just makes it that much harder for the beginning rider to pull off clean take offs, not to mention worrying about stalling the bike in the middle of an intersection. My take on this is that the bikes are lean due to incorrect settings of the idle mixture screws at the factory. Whoever is doing them is not setting them correctly... and to make it worse, they are not setting them incorrectly consistently. *This means some bikes are waaaayy too lean, some sorta* lean, others just right and still others (very few) rich. How many washers you will need will depend on a couple of things. The thickness of the washers you use, the setting of your particular bike's mixture screws from the factory as well as other factors that normally affect jetting. (temp, altitude and humidity) Take all this into account and it is easy to see why there are no golden rules as to how many washers will work best for all bikes. As is the case with all jetting work, experimentation is key to obtaining jetting perfection. I will say, while you have improved your jetting from stock by using the washers, it is far from perfect, but certainly worlds better than it was from off the showroom floor. For many, this will be all they will ever need to do to improve the jetting to make theirs an enjoyable, friendly bike. 4- Come on… at least give me a place to start!!** Okay, okay… These are some very general rule of thumb washer numbers. Expect to have to do this a couple of times if you are not satisfied with the recommendations… 1 washer for a completely stock bike. 1-2 washers for an aftermarket can or system 2-3 washers for an aftermarket system or can with the snorkel removed *5- Some caveats before deciding you should do this…* Not all people who have shimmed their bikes have met with success. There have been a few that actually installed the washers and the bike ran like crap. They ended up taking the washers back out and their bikes run fine without any washers to this day. Remember step #1? Their bikes never stalled from stops and in fact needed little or no choke at start up. These bikes are the few that were set right or a bit rich from the factory. You need to determine if the situations in #1 describe your bike. If it does, it’s a safe bet shimming will improve your bike. If you have never worked on a bike before and would like to do this mod, read the DIY link I posted. Read it (the entire thread!) and understand it before you start tearing your bike apart. Have all the suggested tools available, especially the long #2 Phillips screwdriver. It does take some degree of mechanical skill to accomplish this task and some of the parts you will be dealing with are quite delicate. Just be clean and orderly when you work and you should do fine. Do one carb at a time as you don’t want to mix parts up between the left and right carb as some parts are different between the two. Set aside some time to do this. If it’s your first time tearing the bike apart, plan on 4 hours. Personally, I usually allow double the time on any new project I work on, so for this I would put aside 8 hours just in case something should go wrong. If there are any questions, please post them in this thread and the members of the board who have done this before will be more than happy to answer your questions and/or sooth your fears.