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Old December 27th, 2018, 09:40 AM   #1
Keithb7
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2010 Jetting...In the ball park

Last September after removing the airbox snorkel on my stock 2012, I noticed the bike was acting like it was running lean. Harder starting. Poor acceleration from idle. I bought the bike used, it came with 98 main jets and 38 pilot jets. I put up with it as the riding season was wrapping up here. I planned to re-jet the bike this winter.

Over the xmas holidays, I had time to get it done. I tore the bike down to pull the carbs. I live at about 2350 ft elevation. I decided to go with 42 pilot jets and 105 main jet. I reassembled the bike and flashed it up. It starts easily now. Upon warm up, the bike will rev up with much less hesitation. The higher RPM's come on quickly....However there is snow on the roads here so test riding is out until probably late March, next spring.

I am hearing a slight hesitation when cracking the throttle from off idle still. How can I determine if I am too rich or too lean on the pilot jet? Hard to make any progress without test riding I suppose. Jut wondering if I am in the ball park on the jets.

Stock exhaust and air filter. Just the snorkel removed. Thanks for any tips.

Keith
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Old December 28th, 2018, 10:54 AM   #2
Ceeloo Yello
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42 pilot jet sounds too big to me.
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Old December 28th, 2018, 12:10 PM   #3
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You don't need the bigger Pilot Jets with a stock airbox and pipe. We ran ours with pods and a leaky exhaust with the stock 38s.

We ran 108 Mains. 105s may be too much for you.

I would say you need to adjust the idle mixture with the Idle Mixture screws. With 42 Pilots you won't be very far out - https://faq.ninja250.org/wiki/How_do...dle_mixture%3F

You will always get a hesitation when cracking the throttle hard with CV carbs.

Shimming the needles will richen the midrange slightly - https://faq.ninja250.org/wiki/Washers_for_carb_needles

I'd also sync the carbs if you haven't.

This section may have some helpful info - https://faq.ninja250.org/wiki/Intake
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Old December 28th, 2018, 08:19 PM   #4
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Quote:
Originally Posted by Keithb7 View Post
Last September after removing the airbox snorkel on my stock 2012, I noticed the bike was acting like it was running lean. Harder starting. Poor acceleration from idle. I bought the bike used, it came with 98 main jets and 38 pilot jets. I put up with it as the riding season was wrapping up here. I planned to re-jet the bike this winter.
note that this is a change in behavior. Bike left factory running perfectly, so what changed? Displacement didn't change? Airflow pattern didn't change with full exhaust (slip-ons doesn't really change much), or cam-mods or larger valves.

And higher altitude actually makes mixtures richer due to lower density air.

What you have are clogged carbs that needs complete disassembly, ultrasonic bath in caustic radioactive solvents for weeks, complete flossing of all hidden passages and jets with expanding scrubber wire, along with 10000psi soda blasting. Do search here for "clean carbs ducatiman" for numerous people with same issues.

Don't get cause and effect (symptoms) mixed up. Sure up-sizing jets may cure symptoms temporarily, but you'll need to do it again in couple months. We see it all time, people putting in larger and larger jets to compensate for clogged carbs. But bike still won't run as well as factory-fresh clean condition. It ran perfectly fine when leaving factory, no reason it can't when restored to that conditon.

For reference, most of jetting-DB is for pre-gen bikes. New-gen bikes come from factory with too-rich 11.0:1 or more AFR in high-end with slight leanness in mid-range using 98 jets. My race-bike has all the mods: no snorkel, full exhaust, free-flow intake which results in ~20% more airflow and ~20% more power. But it's still too rich with about 12:1 AFR in high-end. I got dyno-tuned by sponsor Spears Racing and they installed smaller than factory 96 jets to lean out high-end and make even more power. Best power is made around 13.0-13.5:1 AFR and I'm still richer than that.

I suggest you go back to factory jetting with perhaps 1-washer shimmed needles and have your carbs professionally refurbished by ducatiman, you'll be amazed at how much better it runs when restored to factory fresh condition!
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Old December 28th, 2018, 10:25 PM   #5
Dave Wolfe
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Removing the snorkel takes away some of the off-idle and low end torque and adds some power at the high end. Personally I think the top end improvement is due to leaning of the mixture more than anything else but have no data to support that claim.

For me, adjusting the idle mixture screws for best off idle throttle response gave me a noticable improvement.
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Old December 28th, 2018, 11:40 PM   #6
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Originally Posted by Dave Wolfe View Post
Removing the snorkel takes away some of the off-idle and low end torque and adds some power at the high end. Personally I think the top end improvement is due to leaning of the mixture more than anything else but have no data to support that claim.

For me, adjusting the idle mixture screws for best off idle throttle response gave me a noticable improvement.
Yup, hard starting and accelerating from idle is mixture screw adjustment, not mains. And you're right about leaning out high-end for more power. Here's dyno chart with all mods using factory jetting, way, way too rich.



This is before going down to 96 mains, and even then, still too rich. An article where they went down to 95 mains after AreaP full exhaust upgrade (scroll down to "Nuts and bolts" section).

https://www.sportrider.com/2008-kawa...-cheap#page-10

Last futzed with by DannoXYZ; December 29th, 2018 at 12:48 PM.
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Old December 29th, 2018, 10:56 AM   #7
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The vast majority of jet kit users are inclined to add fuel (more is better, much more is better yet) and inevitably end up on the jetting merry go round.

Marketing for the entire USA (or Euro) keep in mind the factory chooses jets for a wide variety of atmospheric conditions, elevations, etc., even compromised to suit both EPA and efficient running. Hence what is supplied may not be be optimal for you in your specific environment.

Reminder of the old school 2 stroke racing tuners (Erv Kanemoto comes to mind) jetted by changing weather conditions at the track...what worked in cool, clear morning practice did not in cloudy, warm afternoon qualifying sessions....needing changes.They seemed to rejet on an hourly basis and were very good at what they did.
If they failed, engines would blow up (leaned out right to the edge of seizure) or races would be lost (lack of power)

Google Erv Kanemoto, a tuning legend
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Old December 29th, 2018, 06:55 PM   #8
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I have a 2012, which should be nearly the same as yours as far as jetting goes (all bikes are slightly different though). I put an Area-P full exhaust on it, removed the snorkel, and the CA emissions junk. I then switched it to a size 95 main jet, which is smaller than the stock of 98, and it's damn near perfect (I had it checked on a dyno with AFR sensor). So no, you don't need bigger jets, you probably need to clean your carbs as others have said.
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Old December 29th, 2018, 09:18 PM   #9
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i agree, i was on the jetting merry go round till danno yanked me off it. i will dropping to 95's too. 98 is ok but i want it all.
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Old December 30th, 2018, 12:46 AM   #10
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i agree, i was on the jetting merry go round till danno yanked me off it. i will dropping to 95's too. 98 is ok but i want it all.
Don't do it! With factory needles, there's lean spot from 6500-8000rpms as seen on dyno-chart above. Going with smaller mains to lean out top-end will cause stumbling in mid-range. Sure shimming needles will help, but will also richen top-end and negate effects of downsizing mains. Back in '80s, I used to grind custom needles on mini-lathe to cure this issue. Nowadays, i just install EFI. However, there is in-between solution:



Leftmost purple vertical-line is needle in jet at closed position.
Middle purple vertical-line is needle in WOT/high-rpm position.

#3 = factory stock New-gen needle
#4 = DynoJet stage-2 needle

Notice DynoJet needle has larger diameter tip than stock with slightly thinner middle? Compared to stock, this leans out high-end while adding fuel to mid-range. This needle along with DynoJet-94/Keihin-95 mains should give you optimum AFR for max-power.

Start with richest clip-position (lowest) for richest mixtue. Need to use wideband or dyno to measure actual AFR (WOT 4th-gear), should around 12:1 in high-end. Lean out mixtures to 12.5-13.0:1 by raising clip one position at time. This will be optimum for street bike while giving you safety margin for bad fuel. Max-power is a little leaner, but extra 0.5hp isn't worth it unless it's race-bike.
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Old December 30th, 2018, 12:52 AM   #11
Keithb7
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Thanks for all the interesting replies. Yes I suppose dirty carbs is indeed a factor. I had read somewhere (on the internet likely, doh!) that Kawi jetted these bikes lean to meet emission standards, maximize fuel economy, and keep the engine easy to handle for new riders. It kind of makes sense. The 250 is one of the most popular bikes for new riders. Maybe just typical internet BS?

I do find that re-jetting this little bike is a fairly time consuming pain in the butt. Lots of things to take apart, however I am getting quicker at it. I will consider a proper full professional carb cleaning. No the quickest nor easiest thing to do shipping them to the USA, here from Canada where I am .
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Old December 30th, 2018, 02:26 AM   #12
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Emissions testing is done at idle and low-load/RPM ranges. The idle-mixture screws are what affects AFR in that operating zone. You'll want to drill out caps that hides those screws in order to adjust starting and idle mixtures. Https://faq.ninja250.org/wiki/How_do...e_idle_mixture

Here's diagram of which adjustment affects which operating zone.
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Old December 30th, 2018, 07:49 AM   #13
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For the general street use 250 owner, i'd advocate setting the pilot screws and leaving well enough alone AFA jetting changes, provided you've got no extenuating circumstances.

Unless you've got access to EGA machine/dyno (really, how many of us do?) ...jumping on the jetting merry go round will require an unreasonable investment in time/effort, trial and error and perhaps even some frustrating guesswork.

Going forward...monitor fuel consumption (a good indicator of fuel/tuning maladies) Using an ethanol treatment/stabilizer these days important as well.

All predicated on truly clear circuits within the carbs. I cringe when bikes sitting for years are sprayed with "start fluid" in a desperate attempt to get them to run for 3-5 seconds. What for? Sitting for years, you should already KNOW carb service is required.
More damage can occur (plastic slides and rubber diaphragms, remember?) than good to come out of futile spraying with nasty chemicals that melt and warp stuff.

Remove and properly service, says I. Properly synch, set pilots then leave well enough alone.
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Old December 30th, 2018, 10:15 AM   #14
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Btw, what has ambient temperatures been in Canada?
I'm visiting my grandma in couple weeks in Montréal; might need to wear pants and maybe jacket...
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Old December 30th, 2018, 05:35 PM   #15
Keithb7
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Ambient temps vary widely from one end of Canada to the other. I am in Western Canada. Sorry I have no idea what's going on in Montreal. That's a long way from here.
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Old December 30th, 2018, 06:16 PM   #16
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Originally Posted by DannoXYZ View Post
Btw, what has ambient temperatures been in Canada?
I'm visiting my grandma in couple weeks in Montréal; might need to wear pants and maybe jacket...
Due to legal and social implications...wearing pants highly suggested!
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Old December 30th, 2018, 07:16 PM   #17
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Ambient temps vary widely from one end of Canada to the other. I am in Western Canada. Sorry I have no idea what's going on in Montreal. That's a long way from here.
Well, I was checking to see what your ambient temperatures are. Around here, any time temps drop below 10C, my bike starts having difficulty starting and needs at least 2-3 minutes of warm-up before I can take off. Confirmed with neighbor that his 2009 250R does same thing. Before this winter set in, we both did "highest-idle speed" adjustment of pilot-screws. So far, it's working lots better than last winter.
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Old December 30th, 2018, 07:19 PM   #18
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Due to legal and social implications...wearing pants highly suggested!
heh, heh... in sunny California, I wear shorts and T-shirts year-round! Although there is photo from university days of me skiing naked @ Squaw Valley...
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Old January 1st, 2019, 09:36 PM   #19
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Originally Posted by maverick9611 View Post
i agree, i was on the jetting merry go round till danno yanked me off it. i will dropping to 95's too. 98 is ok but i want it all.
DynoJet's stage-2 needle isn't available for purchase on its own, BOO!!! I'm investigating other needles with similar profiles. So far, a Harley unit may fit bill. Gonna order it and test in couple weeks. Hmmm, might be excuse to convert my mini-lathe to CNC....
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