Jetting/intake mods - consolidated advice?

adouglas · April 20th, 2010, 02:28 AM

For all those brave pioneers who have blazed the trail of intake and jetting, we salute you.

The risks you've taken and work you've put in are truly appreciated. The thorough documentation you have left behind is invaluable to the rest of us.

However, it's all rather voluminous and scattered, so it's tough for a person like myself to know which direction to take. It seems like I'll be removing and reinstalling the carbs over and over, fighting with airboxes and crappy JIS screws at every turn. And if I do the various mods in stages, I'm going to have to reassess the jetting with each one... more diagnosis, more ripping apart, etc.

As I understand it, these are the things that can be done:
- Shimming the needles
- Rejetting the carbs
- Installing a high-flow stock replacement air filter
- Removing the snorkel
- Removing the airbox
- Installing pod filters
- Plugging the kleen air system

I think that's it. Obviously some of these are pointless if you do others (you can't leave the snorkel on if you rip the airbox out, and shimming the needles is part of rejetting anyway, right)?

So, given the wealth of information we've got here, and if you were to start from stock TODAY knowing what you now know, what would you do? Pretend someone hands you a stock bike, a new exhaust and says "make it work."

- Would you go straight to pod filters and remove the airbox (simpler access in the future, more expense and work up front)?
- Would you plug the kleen air system right away?
- Anything else?

What I'm looking for is not detailed info... that's all documented really well. I'm looking for overall direction.

My goals, in order of priority:

1) To realize the potential of the AreaP Quiet Core exhaust I just bought from the classifieds.
2) To maintain driveability and user-friendliness. This is a daily driver bike, not a race bike. That last tenth of a horsepower doesn't matter to me all that much.
3) To maintain low noise, fuel economy and low environmental impact to the extent possible.

I realize that the third item opposes the other two to some extent. They are in the order of priority.

So, ye brave pioneers with the benefit of hindsight, were I to hand you my bike and exhaust, what would you do to it?

kkim · April 20th, 2010, 04:39 AM

The approach is pretty universal with todays modern emission restricted bikes. You need to basically open up the intake and exhaust portions of the engine. This was my approach to my 250 ninja and also to the recent dirt bikes I've "uncorked". The idea is to make it easier for air to flow from the intake, through the engine and out the exhaust. Correct rejetting will optimize the fuel/air mixture to produce maximum power that your chosen setup requires.

If it were me, I'd desnorkel, install a replacement K&N panel filter into the stock airbox, install a Factory Pro jet kit using stock 98 mains, clip in the 4th position on the needles, adjust air screws, (You might want to install the one step richer pilot jets that are supplied with the newer FP kits), sync carbs, and install the AP exhaust system. Keep in mind jetting is based on my location and is subject to fine tuning, but this is a pretty close baseline of what will work with the mods suggested.

You'll most likely find it necessary to remove the Kleen system once the full exhaust is installed and the bike starts popping on low rpm decel situations.

good luck with playing with your bike. Be sure you are willing to put in the time and effort to fine tune the jetting as this is a time consuming, repetitive exercise. The results are, IMHO, very rewarding.

M-Oorb · April 20th, 2010, 05:07 AM

If I had to do it all over again, I think I would stick with what I have already done. My temp. in South Florida doesnt really change all that much season to season.

As soon as a full exhaust is installed I'd plug up the Kleen air system. Pretty easy to do... disassembling the bike takes more time than actually doing the mod. Pulling the snorkel...also easy and it sounds great IMO. Replacing the filter with a K&N drop in...also simple.

Then I would replace the JIS screws with allen head screws...makes things a lot easier for future Re-jets if you have to. Then I would simply shim the needles...I went with 2 washers. Many re-jet but I found for my needs a simple shimming worked wonders and I have no issues across any part of my power band. It is not as adjustable as jetting but for me I did not see the need to go that route.

Hope that helps! Each person will do his own thing and thats what makes modding great...itd be boring if everyone's 250 was the same.

United through Individuality!

adouglas · April 20th, 2010, 05:58 AM

Quote:

Originally Posted by kkim

The approach is pretty universal with todays modern emission restricted bikes. You need to basically open up the intake and exhaust portions of the engine. This was my approach to my 250 ninja and also to the recent dirt bikes I've "uncorked". The idea is to make it easier for air to flow from the intake, through the engine and out the exhaust. Correct rejetting will optimize the fuel/air mixture to produce maximum power that your chosen setup requires.

Yep. Got that... well understood.

Quote:

Originally Posted by kkim

If it were me, I'd desnorkel, install a replacement K&N panel filter into the stock airbox, install a Factory Pro jet kit using stock 98 mains, clip in the 4th position on the needles, adjust air screws, (You might want to install the one step richer pilot jets that are supplied with the newer FP kits), sync carbs, and install the AP exhaust system. Keep in mind jetting is based on my location and is subject to fine tuning, but this is a pretty close baseline of what will work with the mods suggested.

You'll most likely find it necessary to remove the Kleen system once the full exhaust is installed and the bike starts popping on low rpm decel situations.

Thanks, kkim. That's exactly what I was looking for.

adouglas · April 20th, 2010, 06:03 AM

Quote:

Originally Posted by M-Oorb

United through Individuality!

One of my favorite movie moments, from Python's The Life of Brian. Large numbers of people have mistaken him for the Messiah, and are gathered in the street outside his house. He is standing in the window.

Crowd: [Ecstatic Greetings]

Brian: Good morning!

Crowd: A blessing! A blessing! A blessing!

Brian: Oh, please, please, please, listen! I've got one or two things to say.

Crowd: Tell us! Tell us both of them!

Brian: Look, you've got it all wrong! You don't need to follow me! You don't need to follow anybody! You've got to think for yourselves! You're all individuals!

Crowd: Yes, we're all individuals!

Brian: You're all different!

Crowd: Yes, we are all different!

Homogenous Man: I'm not.

ninja250 · April 20th, 2010, 07:19 AM

Quote:

- Would you go straight to pod filters and remove the airbox (simpler access in the future, more expense and work up front)?
- Would you plug the kleen air system right away?
- Anything else?

1) To realize the potential of the AreaP Quiet Core exhaust I just bought from the classifieds.
2) To maintain driveability and user-friendliness. This is a daily driver bike, not a race bike. That last tenth of a horsepower doesn't matter to me all that much.
3) To maintain low noise, fuel economy and low environmental impact to the extent possible.

1)Removing the airbox will put you in race bike status I think. More gas/air intake and more sound from the intake + the exhaust and you're racing.

2) adding shims makes the bike easier to control in low throttle. Id say that increases driveability.

3)again don't do pods if you want low noise.

I'd do the kleen air since you have the exhaust though.

kkim pretty much nailed it. Don't pull your airbox..

adouglas · April 20th, 2010, 08:36 AM

Yeah, I was actually leaning in the direction of pods just to reduce complexity. What I lacked was clear understanding of the implications of everything. When you look at all those individual DIY threads, every one seems to be a good idea. There's just no context, and you guys have provided exactly that.

My first step is to get the exhaust installed, which I can run with the stock setup according to Area P (I asked).

Next is the snorkel, jet kit and filter, which I'll do all at the same time to minimize the number of variables that change during the process. I'll use kkim's input as my starting point.

If I may humbly suggest... make this simple little thread a sticky or the DIY section so that others about to jump in can benefit from it.

April 20th, 2010, 02:28 AM	#1
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	Jetting/intake mods - consolidated advice? For all those brave pioneers who have blazed the trail of intake and jetting, we salute you. The risks you've taken and work you've put in are truly appreciated. The thorough documentation you have left behind is invaluable to the rest of us. However, it's all rather voluminous and scattered, so it's tough for a person like myself to know which direction to take. It seems like I'll be removing and reinstalling the carbs over and over, fighting with airboxes and crappy JIS screws at every turn. And if I do the various mods in stages, I'm going to have to reassess the jetting with each one... more diagnosis, more ripping apart, etc. As I understand it, these are the things that can be done: - Shimming the needles - Rejetting the carbs - Installing a high-flow stock replacement air filter - Removing the snorkel - Removing the airbox - Installing pod filters - Plugging the kleen air system I think that's it. Obviously some of these are pointless if you do others (you can't leave the snorkel on if you rip the airbox out, and shimming the needles is part of rejetting anyway, right)? So, given the wealth of information we've got here, and if you were to start from stock TODAY knowing what you now know, what would you do? Pretend someone hands you a stock bike, a new exhaust and says "make it work." - Would you go straight to pod filters and remove the airbox (simpler access in the future, more expense and work up front)? - Would you plug the kleen air system right away? - Anything else? What I'm looking for is not detailed info... that's all documented really well. I'm looking for overall direction. My goals, in order of priority: 1) To realize the potential of the AreaP Quiet Core exhaust I just bought from the classifieds. 2) To maintain driveability and user-friendliness. This is a daily driver bike, not a race bike. That last tenth of a horsepower doesn't matter to me all that much. 3) To maintain low noise, fuel economy and low environmental impact to the extent possible. I realize that the third item opposes the other two to some extent. They are in the order of priority. So, ye brave pioneers with the benefit of hindsight, were I to hand you my bike and exhaust, what would you do to it?

April 20th, 2010, 05:07 AM	#3
M-Oorb ninjette.org sage Name: Matt Location: South East Florida/Rutgers University Join Date: Dec 2008 Motorcycle(s): 2008 250r (Fastest Color) Posts: 914	If I had to do it all over again, I think I would stick with what I have already done. My temp. in South Florida doesnt really change all that much season to season. As soon as a full exhaust is installed I'd plug up the Kleen air system. Pretty easy to do... disassembling the bike takes more time than actually doing the mod. Pulling the snorkel...also easy and it sounds great IMO. Replacing the filter with a K&N drop in...also simple. Then I would replace the JIS screws with allen head screws...makes things a lot easier for future Re-jets if you have to. Then I would simply shim the needles...I went with 2 washers. Many re-jet but I found for my needs a simple shimming worked wonders and I have no issues across any part of my power band. It is not as adjustable as jetting but for me I did not see the need to go that route. Hope that helps! Each person will do his own thing and thats what makes modding great...itd be boring if everyone's 250 was the same. United through Individuality! __________________________________________________ Pictures of my ninjette plus...

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April 20th, 2010, 04:39 AM	#2
kkim Join Date: Nov 2008 Posts: Too much.	The approach is pretty universal with todays modern emission restricted bikes. You need to basically open up the intake and exhaust portions of the engine. This was my approach to my 250 ninja and also to the recent dirt bikes I've "uncorked". The idea is to make it easier for air to flow from the intake, through the engine and out the exhaust. Correct rejetting will optimize the fuel/air mixture to produce maximum power that your chosen setup requires. If it were me, I'd desnorkel, install a replacement K&N panel filter into the stock airbox, install a Factory Pro jet kit using stock 98 mains, clip in the 4th position on the needles, adjust air screws, (You might want to install the one step richer pilot jets that are supplied with the newer FP kits), sync carbs, and install the AP exhaust system. Keep in mind jetting is based on my location and is subject to fine tuning, but this is a pretty close baseline of what will work with the mods suggested. You'll most likely find it necessary to remove the Kleen system once the full exhaust is installed and the bike starts popping on low rpm decel situations. good luck with playing with your bike. Be sure you are willing to put in the time and effort to fine tune the jetting as this is a time consuming, repetitive exercise. The results are, IMHO, very rewarding.

April 20th, 2010, 08:36 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	Yeah, I was actually leaning in the direction of pods just to reduce complexity. What I lacked was clear understanding of the implications of everything. When you look at all those individual DIY threads, every one seems to be a good idea. There's just no context, and you guys have provided exactly that. My first step is to get the exhaust installed, which I can run with the stock setup according to Area P (I asked). Next is the snorkel, jet kit and filter, which I'll do all at the same time to minimize the number of variables that change during the process. I'll use kkim's input as my starting point. If I may humbly suggest... make this simple little thread a sticky or the DIY section so that others about to jump in can benefit from it.