Real-World First-time Jetting Questions

The Blue Rider · April 11th, 2011, 08:54 PM

I've been reading all kinds of threads about all the different ways to adjust carburetion. After a whole lot of hemming and hawing between extremes, I think I know what I'm going to do, but I want some validation and guidance.

BACKGROUND (skip this part if you like):

I've been riding for a year. I'm in DFW/North Texas, which I am told is a pretty fast, aggressive corner of the world as far as driving and drivers go. Average around-town speed is about 40mph no matter where you are, average highway traffic speed in my area is 70ish, and merging onto the local highway at 6:45 A.M. is like plummeting downhill on a little sled into a NASCAR race. We do also get windy conditions fairly often which, as we know, can be trouble for the Ninjette. Before somebody says "save your money and buy a bigger bike if this is your trouble", let me make it clear that that won't be happening anytime soon for a number of reasons which I won't get into here. Barring a lottery win, I'll be with my Ninjette for at least another year or two.

About how I ride - it's too early in my riding career to say I have a "style", I think, but basically I like speed, I like having acceleration on tap, I like travel, but I'm not a nut and I don't have any squid or hooligan tendencies. I'm also not always the smoothest hand with the levers; I'm still new to standard transmission and anything I can do to take the roughness out of low-speed maneuvering and throttle response is a big plus. When moving on the road, I do use all of the RPM range in each gear up to about 12K (I stay clear of redline), and my bike is happiest and responsive enough at 10-11K (I hate 9K, I get a weird harmonic at almost exactly that RPM). I don't bother with 6th gear on the highway because I don't feel any power response there either way (accel or decel), and my bike tops out at around 82mph real-world speed, WOT in 5th, allowing for a 10% speedo error. I'm 5'9, 210lbs without gear, shall we say "a bit too wide for my height", and ATGATT, if that's an aerodynamic factor. My riding involves highway time pretty much every time I go out, there's no avoiding it here, and I do like taking day trips out to various places (2-400 miles in a day).

I've identified two areas of concern which I think I can fix with some jetting adjustments.

THE ISSUES:

- First, riding down low, like everything from about 0-20mph and/or up to, say, 6000 RPM, doesn't feel smooth. Coming off of stops, parking lot speeds, low RPM situations, basically the entirety of first gear (I do use all of it!). The response feels grungy and rough, and sometimes a little bit jerky. Some of that is operator error, but things just don't feel smooth while puttering casually or working from zero up to average street speed.

- Second, up at high power/high speed, I feel like the bike is a bit tapped out. Acceleration or "pull" starts getting weak right around the place I start looking for emergency passing power in, say, my car. I'd like just a little bit more guts at upper RPM when I'm already moving at a good pace.

In between the slow and the fast, I don't really feel bothered by anything (except the weird harmonic at 9K). Up through moderate speeds and RPMs she seems to accelerate just fine (If a little slow, since I'm about 50% heavier than the designed rider weight).

MY PLAN:

I've read about every thread I could find on jetting, shimming, kits, exhaust, et cetera. So here is what I THINK I should do about what I want to improve:

1. Install an Area P Quiet Core Carbon Fiber full system. It's big $$, yes, but I dinged up my stock exhaust in a small crash last May and I want to replace it anyway.
2. Pull the snorkel.
3. Remove the Kleen Air system and cap it off with one of those spiffy gold-colored plates.
4. Shim the needles - I think 3 of the 3mm washers would be a good starting point for the above config?
5. Idle mixture adjustment.
6. Synch the carbs.

Undecided/questions:

- What happens when you put on a full exhaust system and change absolutely nothing else? Are you just adding nicer sound, or is there a performance benefit even without intake or mixture adjustment?

- How about a K&N Panel filter? Would adding this in addition to removing the snorkel let in even more air (leaning out mixture), or is it true what they say about these things being a waste of money?

- Would pulling the snorkel cause any damage to low-end performance? I understand that the airbox and snorkel are designed to channel the incoming air in a way that usually benefits low-end power. I don't want to grunge up things even worse down at the bottom, and I tend to think the Kawasaki engineers knew what they were doing when they put the snorkel in. I've also read in various threads how tearing out the airbox and/or snorkel can sometimes complicate rejetting woes. I want some reassurance that this is worth doing and has a real positive effect, when balanced by appropriate enrichment elsewhere in the fuel/air system.

- Factory Pro needles. Could I get a jet kit and use just the needles for now, instead of shimming the stock needles? Meaning, would needles with an aftermarket shape provide better response than stock + shimmed? I ask because it would seem easier to adjust idle mixture for two identical needles, rather than the mis-matched stock needles, and if I find that I want to get more involved with jetting changes or airbox removal later on, I'd have the parts already on hand. Or, are kit needles really meant to be used as part of the full approach of changing pilot & mains and fine tuning, using the rest of the supplied kit?

Airbox tear-out and Uni pods with a full re-jet just doesn't sound like a good idea right now. I'm looking for a solution I could implement in a weekend's work; I don't have the time or the inclination to mess around with multiple carb removal/installation cycles.

Thanks for any help!

kkim · April 11th, 2011, 10:13 PM

Quote:

Originally Posted by Shalev

I don't have the time or the inclination to mess around with multiple carb removal/installation cycles.

then I would recommend you leave it stock. Anytime you change something on the bike that requires the need to rejet, you'll be looking at going in at least a couple of times at least to get things "right".

you're best bet, if you want to do this only once, is to check over the jetting database, choose a configuration someone else has and copy their setup. no guaranty it will work for you, but at least it will be a close starting point.

The Blue Rider · April 12th, 2011, 10:07 AM

I read the shimming threads, and shimming (or dropping in some kit needles?) doesn't seem difficult. If I understand correctly, I could make the changes I want without having to pull the airbox and tear down the carbs. I've had the plastics off, I've changed oil, etc. so the mechanical work doesn't bother me; I'm really looking for the easiest way to clean up the power curve, and shimming seems to be the ticket.

kkim · April 12th, 2011, 10:31 AM

yes, but be ready to add or subtract a shim if it isn't right the first time. shimming is the easiest way to address the power "shortcomings" of a stock ninja, but be prepared to do it a couple of times to get it right.

the next easiest thing would be to drop some aftermarket needles in place of the stock needles. even then, you might have to adjust the clip position.

fine tuning jetting is a time consuming, headache of a job.

saying that, most that shim their bikes end up liking the results and are most times glad they did it... all except the ones that had installation errors, which can lead to nightmares.

April 11th, 2011, 08:54 PM	#1
The Blue Rider ninjette.org member Name: Terry Location: Euless, TX Join Date: Dec 2010 Motorcycle(s): '09 Ninja 250R Posts: 43	Real-World First-time Jetting Questions I've been reading all kinds of threads about all the different ways to adjust carburetion. After a whole lot of hemming and hawing between extremes, I think I know what I'm going to do, but I want some validation and guidance. BACKGROUND (skip this part if you like): I've been riding for a year. I'm in DFW/North Texas, which I am told is a pretty fast, aggressive corner of the world as far as driving and drivers go. Average around-town speed is about 40mph no matter where you are, average highway traffic speed in my area is 70ish, and merging onto the local highway at 6:45 A.M. is like plummeting downhill on a little sled into a NASCAR race. We do also get windy conditions fairly often which, as we know, can be trouble for the Ninjette. Before somebody says "save your money and buy a bigger bike if this is your trouble", let me make it clear that that won't be happening anytime soon for a number of reasons which I won't get into here. Barring a lottery win, I'll be with my Ninjette for at least another year or two. About how I ride - it's too early in my riding career to say I have a "style", I think, but basically I like speed, I like having acceleration on tap, I like travel, but I'm not a nut and I don't have any squid or hooligan tendencies. I'm also not always the smoothest hand with the levers; I'm still new to standard transmission and anything I can do to take the roughness out of low-speed maneuvering and throttle response is a big plus. When moving on the road, I do use all of the RPM range in each gear up to about 12K (I stay clear of redline), and my bike is happiest and responsive enough at 10-11K (I hate 9K, I get a weird harmonic at almost exactly that RPM). I don't bother with 6th gear on the highway because I don't feel any power response there either way (accel or decel), and my bike tops out at around 82mph real-world speed, WOT in 5th, allowing for a 10% speedo error. I'm 5'9, 210lbs without gear, shall we say "a bit too wide for my height", and ATGATT, if that's an aerodynamic factor. My riding involves highway time pretty much every time I go out, there's no avoiding it here, and I do like taking day trips out to various places (2-400 miles in a day). I've identified two areas of concern which I think I can fix with some jetting adjustments. THE ISSUES: - First, riding down low, like everything from about 0-20mph and/or up to, say, 6000 RPM, doesn't feel smooth. Coming off of stops, parking lot speeds, low RPM situations, basically the entirety of first gear (I do use all of it!). The response feels grungy and rough, and sometimes a little bit jerky. Some of that is operator error, but things just don't feel smooth while puttering casually or working from zero up to average street speed. - Second, up at high power/high speed, I feel like the bike is a bit tapped out. Acceleration or "pull" starts getting weak right around the place I start looking for emergency passing power in, say, my car. I'd like just a little bit more guts at upper RPM when I'm already moving at a good pace. In between the slow and the fast, I don't really feel bothered by anything (except the weird harmonic at 9K). Up through moderate speeds and RPMs she seems to accelerate just fine (If a little slow, since I'm about 50% heavier than the designed rider weight). MY PLAN: I've read about every thread I could find on jetting, shimming, kits, exhaust, et cetera. So here is what I THINK I should do about what I want to improve: 1. Install an Area P Quiet Core Carbon Fiber full system. It's big $$, yes, but I dinged up my stock exhaust in a small crash last May and I want to replace it anyway. 2. Pull the snorkel. 3. Remove the Kleen Air system and cap it off with one of those spiffy gold-colored plates. 4. Shim the needles - I think 3 of the 3mm washers would be a good starting point for the above config? 5. Idle mixture adjustment. 6. Synch the carbs. Undecided/questions: - What happens when you put on a full exhaust system and change absolutely nothing else? Are you just adding nicer sound, or is there a performance benefit even without intake or mixture adjustment? - How about a K&N Panel filter? Would adding this in addition to removing the snorkel let in even more air (leaning out mixture), or is it true what they say about these things being a waste of money? - Would pulling the snorkel cause any damage to low-end performance? I understand that the airbox and snorkel are designed to channel the incoming air in a way that usually benefits low-end power. I don't want to grunge up things even worse down at the bottom, and I tend to think the Kawasaki engineers knew what they were doing when they put the snorkel in. I've also read in various threads how tearing out the airbox and/or snorkel can sometimes complicate rejetting woes. I want some reassurance that this is worth doing and has a real positive effect, when balanced by appropriate enrichment elsewhere in the fuel/air system. - Factory Pro needles. Could I get a jet kit and use just the needles for now, instead of shimming the stock needles? Meaning, would needles with an aftermarket shape provide better response than stock + shimmed? I ask because it would seem easier to adjust idle mixture for two identical needles, rather than the mis-matched stock needles, and if I find that I want to get more involved with jetting changes or airbox removal later on, I'd have the parts already on hand. Or, are kit needles really meant to be used as part of the full approach of changing pilot & mains and fine tuning, using the rest of the supplied kit? Airbox tear-out and Uni pods with a full re-jet just doesn't sound like a good idea right now. I'm looking for a solution I could implement in a weekend's work; I don't have the time or the inclination to mess around with multiple carb removal/installation cycles. Thanks for any help!

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April 12th, 2011, 10:07 AM	#3
The Blue Rider ninjette.org member Name: Terry Location: Euless, TX Join Date: Dec 2010 Motorcycle(s): '09 Ninja 250R Posts: 43	I read the shimming threads, and shimming (or dropping in some kit needles?) doesn't seem difficult. If I understand correctly, I could make the changes I want without having to pull the airbox and tear down the carbs. I've had the plastics off, I've changed oil, etc. so the mechanical work doesn't bother me; I'm really looking for the easiest way to clean up the power curve, and shimming seems to be the ticket.

April 12th, 2011, 10:31 AM	#4
kkim Join Date: Nov 2008 Posts: Too much.	yes, but be ready to add or subtract a shim if it isn't right the first time. shimming is the easiest way to address the power "shortcomings" of a stock ninja, but be prepared to do it a couple of times to get it right. the next easiest thing would be to drop some aftermarket needles in place of the stock needles. even then, you might have to adjust the clip position. fine tuning jetting is a time consuming, headache of a job. saying that, most that shim their bikes end up liking the results and are most times glad they did it... all except the ones that had installation errors, which can lead to nightmares.