Just got the Yoshimura Exhaust and I don't know what to do?

ckoolmike · May 6th, 2010, 06:03 AM

Hi guys...

need your help. I just purchased the Yoshimura slip on exhaust and I want to install it but i keep reading (and not fully understanding) about shimming the needles and installing a jet kit? Sorry for my ignorance but i read a lot of the threads and yet to understand what i really need to do.

If i need a factory pro kit then so be it. Does that mean i need to shim the needles too? So confused. Sorry pls help!!

Would love to install this tonight. So if someone can help me and tell me what to do ...that'll be great.

I live in Ontario, Canada!

tabogon · May 6th, 2010, 06:18 AM

Shimming is a crued way of "jetting" the carbs. You can just shim the needles, but it won't give you the ability to fine tune the carbs for best performance. Although shimming is VERY cheap and extremely easy.

If you are finiky about working on the carbs, then installing a jet kit at the dealership is also an option, but will cost you the price of the kit, dealership labor, and tuning.

I have yet to get my exhaust and not really sure if I will anytime soon ( I like the sound of the bike now after shimming and removing the snorkel) however I know I can add another shim to each carb when I do install an exhaust and it will be fine.

I am not too sure about the atmosphere in Canada and the altitude there, you might be better off jetting the carbs, but I will let another Canadian answer that one.

adouglas · May 6th, 2010, 06:54 AM

Sorry for the long post... hope this helps.

Short answer: Changing the needle height (which is what shimming does) is part of what you do when you install a jet kit, so the two activities are redundant. The difference is that if you shim the stock needles, all you need to do is buy a few 12-cent washers, but if you rejet you need to buy a $90 jet kit.

Shorter answer: You don't need to do anything before you install the Yosh can. You won't hurt your bike, but you won't get maximum benefit either. Put it on and then think about jetting or shimming.

But read on.

Step back a minute and look at the big picture. I suspect you're getting too close to the problem and can't see the trees for the forest. I think you need to understand why you're doing these things... that will guide you as you decide what to do.

The goal is to increase the bike's power while maintaining or even improving driveability, right? So how do you do that in a broad sense?

Because an internal combustion engine in a certain sense is just a big gasoline-powered air pump, to make more power you need to pump more air. Which means you need to reduce restrictions on the air going in (intake) and the air going out (exhaust).

(Think of it this way... purse your lips and inhale strongly through them. You have to work hard to do it. Now open your mouth wide and inhale. Much easier... less restriction, so you're not expending energy to overcome it.)

Okay, so you can open up the intake and open up the exhaust, but that's not the whole story. An internal combustion engine needs to have the right balance of air to fuel to function properly, and when you go messing with the intake and exhaust you're changing that delicate balance because you're adding more air to the equation without adding more fuel to compensate. Therefore you need to adjust the fuel system (carburetors) to restore the balance of air to fuel.

That is the purpose of rejetting, which is about more than just jets. It's also about the needles. What you're doing is changing how much fuel the carb feeds to the engine when you open the throttle.

Your goal with rejetting is to find the right combination of jets, needle position and mixture screw settings to make your bike produce its best power and driveability given the changes you've made to your intake and exhaust.

Now, take it down one more level. If you've read all the threads you know that different parts of the carb affect the fuel flow at different throttle openings. The main jets control wide-open-throttle fuel flow. The needle position (and shape) affects the midrange. The pilot jets and screws affect the low end.

So when you install a jet kit, you're doing the whole thing... changing the main jet, changing the needle height (and the needles themselves), and maybe changing the pilot jet too.

When you shim the stock needles, you're doing part of what you do when you install a jet kit. You're playing with the midrange, which is where the bike spends most of its time anyway.

To get the maximum result, you modify your intake (e.g., pull the snorkel and install a K&N air filter, or yank the whole airbox and put pod filters on it), put on a full exhaust including header, and rejet so the bike works properly.

To get better driveability and midrange power, you do part of the job... you shim the needles.

Caveat: I haven't rejetted my bike yet, though I have installed a full exhaust. I welcome corrections by those who know more about this than I do.

tabogon · May 6th, 2010, 07:04 AM

Great post Andrew

That has to be one of the best descriptions of how and ICE works!

ckoolmike · May 6th, 2010, 07:32 AM

Quote:

Originally Posted by adouglas

Sorry for the long post... hope this helps.

Short answer: Changing the needle height (which is what shimming does) is part of what you do when you install a jet kit, so the two activities are redundant. The difference is that if you shim the stock needles, all you need to do is buy a few 12-cent washers, but if you rejet you need to buy a $90 jet kit.

Shorter answer: You don't need to do anything before you install the Yosh can. You won't hurt your bike, but you won't get maximum benefit either. Put it on and then think about jetting or shimming.

But read on.

Step back a minute and look at the big picture. I suspect you're getting too close to the problem and can't see the trees for the forest. I think you need to understand why you're doing these things... that will guide you as you decide what to do.

The goal is to increase the bike's power while maintaining or even improving driveability, right? So how do you do that in a broad sense?

Because an internal combustion engine in a certain sense is just a big gasoline-powered air pump, to make more power you need to pump more air. Which means you need to reduce restrictions on the air going in (intake) and the air going out (exhaust).

(Think of it this way... purse your lips and inhale strongly through them. You have to work hard to do it. Now open your mouth wide and inhale. Much easier... less restriction, so you're not expending energy to overcome it.)

Okay, so you can open up the intake and open up the exhaust, but that's not the whole story. An internal combustion engine needs to have the right balance of air to fuel to function properly, and when you go messing with the intake and exhaust you're changing that delicate balance because you're adding more air to the equation without adding more fuel to compensate. Therefore you need to adjust the fuel system (carburetors) to restore the balance of air to fuel.

That is the purpose of rejetting, which is about more than just jets. It's also about the needles. What you're doing is changing how much fuel the carb feeds to the engine when you open the throttle.

Your goal with rejetting is to find the right combination of jets, needle position and mixture screw settings to make your bike produce its best power and driveability given the changes you've made to your intake and exhaust.

Now, take it down one more level. If you've read all the threads you know that different parts of the carb affect the fuel flow at different throttle openings. The main jets control wide-open-throttle fuel flow. The needle position (and shape) affects the midrange. The pilot jets and screws affect the low end.

So when you install a jet kit, you're doing the whole thing... changing the main jet, changing the needle height (and the needles themselves), and maybe changing the pilot jet too.

When you shim the stock needles, you're doing part of what you do when you install a jet kit. You're playing with the midrange, which is where the bike spends most of its time anyway.

To get the maximum result, you modify your intake (e.g., pull the snorkel and install a K&N air filter, or yank the whole airbox and put pod filters on it), put on a full exhaust including header, and rejet so the bike works properly.

To get better driveability and midrange power, you do part of the job... you shim the needles.

Caveat: I haven't rejetted my bike yet, though I have installed a full exhaust. I welcome corrections by those who know more about this than I do.

I thank you sooo much for helping me understand this process. You're awesome man.

ckoolmike · May 6th, 2010, 07:33 AM

Quote:

Originally Posted by tabogon

Shimming is a crued way of "jetting" the carbs. You can just shim the needles, but it won't give you the ability to fine tune the carbs for best performance. Although shimming is VERY cheap and extremely easy.

If you are finiky about working on the carbs, then installing a jet kit at the dealership is also an option, but will cost you the price of the kit, dealership labor, and tuning.

I have yet to get my exhaust and not really sure if I will anytime soon ( I like the sound of the bike now after shimming and removing the snorkel) however I know I can add another shim to each carb when I do install an exhaust and it will be fine.

I am not too sure about the atmosphere in Canada and the altitude there, you might be better off jetting the carbs, but I will let another Canadian answer that one.

Thanks for your help too tabogon

adouglas · May 6th, 2010, 07:45 AM

Something that's peripherally related.

If you screw things up and run the bike way too lean, you CAN damage or even destroy your engine. Overly lean engines run really hot.

So don't open up the intake (introduce more air, which makes the mixture too lean) without rejetting too.

Putting on a less restrictive exhaust doesn't change the input side of things. So your aftermarket exhaust won't endanger your bike IMHO.

Actually, since it's a slip-on, it probably doesn't remove that much restriction anyway. You've still got the stock header.

Again, if I'm off target here, someone who knows more please jump in and correct me.

shift_6 · May 6th, 2010, 08:54 AM

most of our bikes run lean from the factory. i would shim the needles for benefit if you dont wanna buy a jet kit. when i first got my bike, it felt like it wanted to bog down in certain rpm's, so i shimmed the needles when i first put on my slip on and it felt a lot better.

off topic: i love this damn bike. its so nimble!

pm: Hokie11 he has extra washers. all you have to do is send him a self addressed stamp envelope asking for 4-6 washers and hell send you some for free!

HKr1 · May 6th, 2010, 10:12 AM

Stock needles suck! Drop some aftermarket needles in, and you will be good to go for your sett up

Momaru · May 6th, 2010, 12:15 PM

Quote:

Originally Posted by adouglas

Sorry for the long post... hope this helps.

Short answer: Changing the needle height (which is what shimming does) is part of what you do when you install a jet kit, so the two activities are redundant. The difference is that if you shim the stock needles, all you need to do is buy a few 12-cent washers, but if you rejet you need to buy a $90 jet kit.

Shorter answer: You don't need to do anything before you install the Yosh can. You won't hurt your bike, but you won't get maximum benefit either. Put it on and then think about jetting or shimming.

But read on.

Step back a minute and look at the big picture. I suspect you're getting too close to the problem and can't see the trees for the forest. I think you need to understand why you're doing these things... that will guide you as you decide what to do.

The goal is to increase the bike's power while maintaining or even improving driveability, right? So how do you do that in a broad sense?

Because an internal combustion engine in a certain sense is just a big gasoline-powered air pump, to make more power you need to pump more air. Which means you need to reduce restrictions on the air going in (intake) and the air going out (exhaust).

(Think of it this way... purse your lips and inhale strongly through them. You have to work hard to do it. Now open your mouth wide and inhale. Much easier... less restriction, so you're not expending energy to overcome it.)

Okay, so you can open up the intake and open up the exhaust, but that's not the whole story. An internal combustion engine needs to have the right balance of air to fuel to function properly, and when you go messing with the intake and exhaust you're changing that delicate balance because you're adding more air to the equation without adding more fuel to compensate. Therefore you need to adjust the fuel system (carburetors) to restore the balance of air to fuel.

That is the purpose of rejetting, which is about more than just jets. It's also about the needles. What you're doing is changing how much fuel the carb feeds to the engine when you open the throttle.

Your goal with rejetting is to find the right combination of jets, needle position and mixture screw settings to make your bike produce its best power and driveability given the changes you've made to your intake and exhaust.

Now, take it down one more level. If you've read all the threads you know that different parts of the carb affect the fuel flow at different throttle openings. The main jets control wide-open-throttle fuel flow. The needle position (and shape) affects the midrange. The pilot jets and screws affect the low end.

So when you install a jet kit, you're doing the whole thing... changing the main jet, changing the needle height (and the needles themselves), and maybe changing the pilot jet too.

When you shim the stock needles, you're doing part of what you do when you install a jet kit. You're playing with the midrange, which is where the bike spends most of its time anyway.

To get the maximum result, you modify your intake (e.g., pull the snorkel and install a K&N air filter, or yank the whole airbox and put pod filters on it), put on a full exhaust including header, and rejet so the bike works properly.

To get better driveability and midrange power, you do part of the job... you shim the needles.

Caveat: I haven't rejetted my bike yet, though I have installed a full exhaust. I welcome corrections by those who know more about this than I do.

Excellent explanation Andrew. My (admittedly somewhat limited) experience rejetting agrees well with your statement. Might consider putting that on the wiki to help folks out.

One addition though: the carbs are set up asymmetrically from the factory and you'll want to resynchronize them with most if not all jetting alterations to ensure each cylinder is taking it's share of the workload.

kkim · May 6th, 2010, 01:48 PM

Great post, Andrew. Now add it to the wiki.

Haider87 · May 9th, 2010, 02:01 AM

I have a stage 3 factory pro jet kit and a yoshi pipe. Here's what it sounds like if you need some inspiration, it was definitely worth the extra cheddar.

http://www.youtube.com/watch?v=_hx9bBXinVg

ckoolmike · May 10th, 2010, 09:48 AM

Anybody from Toronto, Ontario, Canada know where i can pick some up?

Checked out source and home depot with no luck.

thanks in advance.

ckoolmike · May 11th, 2010, 11:08 AM

So i installed the Yosh slip on yesterday. No jet kit, shimming and have not removed snorkle. The bike runs smooth. I still require the choke on while starting the bike and after a minute, it revs from 1500 rpm to 4000 rpm so that's when i remove the choke.

1st gear is not sluggish and i feel the extra hp. Obviously the kicker is the sound of the yosh slip on. It's EXACTLY what i wanted with a deep throttle sound. It makes the stop exhaust sound like a lawnmower.

I am not sure if i need to tweak anything with the bike. Will i cause any damage if i don't shim the needles and remove the snorkle?

Thanks all for your help.

May 6th, 2010, 06:03 AM	#1
ckoolmike ninjette.org newbie Name: Mike Location: Toronto Join Date: Feb 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: 8	Just got the Yoshimura Exhaust and I don't know what to do? Hi guys... need your help. I just purchased the Yoshimura slip on exhaust and I want to install it but i keep reading (and not fully understanding) about shimming the needles and installing a jet kit? Sorry for my ignorance but i read a lot of the threads and yet to understand what i really need to do. If i need a factory pro kit then so be it. Does that mean i need to shim the needles too? So confused. Sorry pls help!! Would love to install this tonight. So if someone can help me and tell me what to do ...that'll be great. I live in Ontario, Canada!

May 6th, 2010, 08:54 AM	#8
shift_6 ninjette.org member Name: SHIFT Location: QUEENS, NYC Join Date: Jun 2009 Motorcycle(s): 08 Candy Plasma Blue Posts: 125	most of our bikes run lean from the factory. i would shim the needles for benefit if you dont wanna buy a jet kit. when i first got my bike, it felt like it wanted to bog down in certain rpm's, so i shimmed the needles when i first put on my slip on and it felt a lot better. off topic: i love this damn bike. its so nimble! pm: Hokie11 he has extra washers. all you have to do is send him a self addressed stamp envelope asking for 4-6 washers and hell send you some for free! __________________________________________________ Real HIP HOP is not on the radio \| SHIFT the MC \| 3,100 Channel Views & Rising \| Updated April 18,2010

May 10th, 2010, 09:48 AM	#13
ckoolmike ninjette.org newbie Name: Mike Location: Toronto Join Date: Feb 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: 8	3mm washers? Anybody from Toronto, Ontario, Canada know where i can pick some up? Checked out source and home depot with no luck. thanks in advance.

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May 6th, 2010, 06:18 AM	#2
tabogon ninjette.org guru Name: Josh Location: CT Join Date: Apr 2010 Motorcycle(s): 2010 Ninja 250R (Metallic Island Blue) Posts: 262	Shimming is a crued way of "jetting" the carbs. You can just shim the needles, but it won't give you the ability to fine tune the carbs for best performance. Although shimming is VERY cheap and extremely easy. If you are finiky about working on the carbs, then installing a jet kit at the dealership is also an option, but will cost you the price of the kit, dealership labor, and tuning. I have yet to get my exhaust and not really sure if I will anytime soon ( I like the sound of the bike now after shimming and removing the snorkel) however I know I can add another shim to each carb when I do install an exhaust and it will be fine. I am not too sure about the atmosphere in Canada and the altitude there, you might be better off jetting the carbs, but I will let another Canadian answer that one.

May 6th, 2010, 06:54 AM	#3
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Sorry for the long post... hope this helps. Short answer: Changing the needle height (which is what shimming does) is part of what you do when you install a jet kit, so the two activities are redundant. The difference is that if you shim the stock needles, all you need to do is buy a few 12-cent washers, but if you rejet you need to buy a $90 jet kit. Shorter answer: You don't need to do anything before you install the Yosh can. You won't hurt your bike, but you won't get maximum benefit either. Put it on and then think about jetting or shimming. But read on. Step back a minute and look at the big picture. I suspect you're getting too close to the problem and can't see the trees for the forest. I think you need to understand why you're doing these things... that will guide you as you decide what to do. The goal is to increase the bike's power while maintaining or even improving driveability, right? So how do you do that in a broad sense? Because an internal combustion engine in a certain sense is just a big gasoline-powered air pump, to make more power you need to pump more air. Which means you need to reduce restrictions on the air going in (intake) and the air going out (exhaust). (Think of it this way... purse your lips and inhale strongly through them. You have to work hard to do it. Now open your mouth wide and inhale. Much easier... less restriction, so you're not expending energy to overcome it.) Okay, so you can open up the intake and open up the exhaust, but that's not the whole story. An internal combustion engine needs to have the right balance of air to fuel to function properly, and when you go messing with the intake and exhaust you're changing that delicate balance because you're adding more air to the equation without adding more fuel to compensate. Therefore you need to adjust the fuel system (carburetors) to restore the balance of air to fuel. That is the purpose of rejetting, which is about more than just jets. It's also about the needles. What you're doing is changing how much fuel the carb feeds to the engine when you open the throttle. Your goal with rejetting is to find the right combination of jets, needle position and mixture screw settings to make your bike produce its best power and driveability given the changes you've made to your intake and exhaust. Now, take it down one more level. If you've read all the threads you know that different parts of the carb affect the fuel flow at different throttle openings. The main jets control wide-open-throttle fuel flow. The needle position (and shape) affects the midrange. The pilot jets and screws affect the low end. So when you install a jet kit, you're doing the whole thing... changing the main jet, changing the needle height (and the needles themselves), and maybe changing the pilot jet too. When you shim the stock needles, you're doing part of what you do when you install a jet kit. You're playing with the midrange, which is where the bike spends most of its time anyway. To get the maximum result, you modify your intake (e.g., pull the snorkel and install a K&N air filter, or yank the whole airbox and put pod filters on it), put on a full exhaust including header, and rejet so the bike works properly. To get better driveability and midrange power, you do part of the job... you shim the needles. Caveat: I haven't rejetted my bike yet, though I have installed a full exhaust. I welcome corrections by those who know more about this than I do.

May 6th, 2010, 07:04 AM	#4
tabogon ninjette.org guru Name: Josh Location: CT Join Date: Apr 2010 Motorcycle(s): 2010 Ninja 250R (Metallic Island Blue) Posts: 262	Great post Andrew That has to be one of the best descriptions of how and ICE works!

May 6th, 2010, 07:45 AM	#7
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Something that's peripherally related. If you screw things up and run the bike way too lean, you CAN damage or even destroy your engine. Overly lean engines run really hot. So don't open up the intake (introduce more air, which makes the mixture too lean) without rejetting too. Putting on a less restrictive exhaust doesn't change the input side of things. So your aftermarket exhaust won't endanger your bike IMHO. Actually, since it's a slip-on, it probably doesn't remove that much restriction anyway. You've still got the stock header. Again, if I'm off target here, someone who knows more please jump in and correct me.

May 6th, 2010, 10:12 AM	#9
HKr1 IC2(SW) Name: Kerry Location: Pensacola Join Date: Nov 2008 Motorcycle(s): . Posts: A lot.	Stock needles suck! Drop some aftermarket needles in, and you will be good to go for your sett up

May 6th, 2010, 01:48 PM	#11
kkim Join Date: Nov 2008 Posts: Too much.	Great post, Andrew. Now add it to the wiki.

May 9th, 2010, 02:01 AM	#12
Haider87 Learning by doing Name: Haider Location: Berkeley, Ca Join Date: Apr 2010 Motorcycle(s): '08 Ninja 250R Posts: 67	I have a stage 3 factory pro jet kit and a yoshi pipe. Here's what it sounds like if you need some inspiration, it was definitely worth the extra cheddar. http://www.youtube.com/watch?v=_hx9bBXinVg

May 11th, 2010, 11:08 AM	#14
ckoolmike ninjette.org newbie Name: Mike Location: Toronto Join Date: Feb 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: 8	So i installed the Yosh slip on yesterday. No jet kit, shimming and have not removed snorkle. The bike runs smooth. I still require the choke on while starting the bike and after a minute, it revs from 1500 rpm to 4000 rpm so that's when i remove the choke. 1st gear is not sluggish and i feel the extra hp. Obviously the kicker is the sound of the yosh slip on. It's EXACTLY what i wanted with a deep throttle sound. It makes the stop exhaust sound like a lawnmower. I am not sure if i need to tweak anything with the bike. Will i cause any damage if i don't shim the needles and remove the snorkle? Thanks all for your help.