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Old July 12th, 2019, 09:47 PM   #1
Seirra117th
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Arrow air filter made bike lean or rich?

hope this post helps others understand how to tune fuel/air ratio

bikes....2008 green machine 250r ex250j 25000k's

have no history from PO

have fixed most problems and can idle nicely, ride only in 1st and 2nd atm due to no rego

so i needed a new air filter the form one is falling apart....i decided to get a k&n style panal hiflow filter from ebay

i installed it and straight away problem after blipping the throttle. it would drop below idle.......sit there.....then slowly come up if it didnt go to stall.......didnt attempt to ride it but normally pulls from a stop at 3000rpm with little drop in rpm

the bike has snorkle removed and yoshi slip on.....stock jets and pilots set at factory and idle set to around 1350......so far had run extremely well and starts up fine in da cold with short choke times......(in Australia and its winter here atm)

im keen on adding the new filter and was thinking its made more air flow so a LEANER mixture.......so i was thinking shimming stock needles with 2 washers.......aswell as increase pilots by 1/4 turn each.......making then L.2 3/4 R.2 total turns out.......if nit pilots out by 1/2 a turn

whats everyones thoughts?
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Old July 13th, 2019, 01:09 AM   #2
59096
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Hi Daniel,

When you say it has the snorkel removed are you referring to the piece with two holes in it that fits into the rear top of the air box that you remove to service the air filter? I have found that even small changes to the intake or the exhaust can upset the carbs. I drilled four 10mm holes in the end of each of the stock mufflers and that very small change caused a loss of mid range so I would expect the Yoshi slip ons to have some effect as well as the K & N air filter. From your description the problem so far is only evident in the idle circuit where it transitions as you open the throttle. Sounds like it is now running lean there and shimming the needles should help. You might find that it is also effected in the mid to high range and you might have to look at bigger main jets. There are plenty on this forum much more experienced than me in this area and I am sure your problem will be solved.

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Old July 13th, 2019, 02:33 AM   #3
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MOTY - 2018, MOTM - Nov '17
Carbs need thorough cleaning.

None of those mods makes much difference in flow at idle-speeds that will throw off AFR (they will make difference at WOT & 13000 rpms).. Unless you actually get a measured AFR number from wideband O2-sensor, do not guess or assume anything about AFR. Also understand what various mods do. Shimming needles does nothing for idle.

Your pilot jet and emulsion tube's bleed holes are not clear. Also hole leading from pilot jet to carb-venturi is most likely obstructed. Spray carb cleaners DO NOT work. You need ultrasonic cleaner soaking with real cleaning solutions along with mechanical flossing using guitar wire followed with soda blasting.

Don't compensate for clogged jets and circuits by blindly dumping in more petrol. You'll have to continually add more needle shims and go to larger and larger jets over time as clog gets worse and worse. Fix actual problem, not compensating for symptoms. Clean those carbs and restore them back to factory-fresh conditions. Then bike's idle and throttle-blip behavior will be factory-fresh as when it first rolled off showroom floor.
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Old July 13th, 2019, 02:53 AM   #4
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I had similar issues on both my 2008 street bike and my 2009 race bike when I first got them. Wasted over $100 on spray carb cleaners and still bad idle and hiccup when opening throttle. Sent street bike's carb to ducatiman for refurb which made bike run like brand new! For race bike, I did complete carb disassemble down to every last nut & bolt for scrubbing, ultrasonic soaking, wire flossing and soda blasting. My race bike has about 22% more power than stock (25.6hp -> 32hp) with following mods:

- snorkel delete
- K&N filter
- full Tyga exhaust
- D-ported head

To fine-tune AFR on race bike, I downsized main-jets and used un-shimmed Dynojet needle to lean out high-end even more. My street bike has 2-sizes smaller main jets with snorkel delete and K&N filter. P!ease look at dyno-chart on this thread for actual AFR readings from dyno-testing along with chart showing which carb-adjustments affects various operating zones.

https://www.ninjette.org/forums/showthread.php?t=335914

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Old July 13th, 2019, 03:02 PM   #5
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Did you oil the filter?
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Old July 13th, 2019, 05:13 PM   #6
Seirra117th
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yes filter oiled with k&n oil
yes SNORKAL removed
and yes the bike idles perfect with the old filter back in

so this is why im confused.......

some say the filter will not affect AFR
and yet other do say that........so still confused as too who is right
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Old July 13th, 2019, 08:27 PM   #7
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MOTY - 2018, MOTM - Nov '17
Try 3rd test with no filter.
Also look for spots where snails may have snuck into your intake.
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Old July 13th, 2019, 08:48 PM   #8
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Quote:
Originally Posted by Seirra117th View Post
yes filter oiled with k&n oil
yes SNORKAL removed
and yes the bike idles perfect with the old filter back in

so this is why im confused.......

some say the filter will not affect AFR
and yet other do say that........so still confused as too who is right
Should be obvious. If the bike idles perfectly with the old filter back in and idles badly with the hi flow installed it means that the hi flow filter setup is causing the problem. Either run with the old filter and put the snorkle back in or do what ever carb tuning is necessary to suit the hi flow. Be prepared to remove and replace the carbs multiple times in doing this. The tuning is right on mine (which it is because everything is standard) and I leave things well alone - to many chances of damaging diaphragms, vacuum hoses and then never getting it exactly right through the whole range (which it is when everything is standard and operating correctly). Just a thought!
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Old July 13th, 2019, 09:07 PM   #9
Seirra117th
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thanks but i thought that danny disagrees with that.....hence the confusion......and i totally get what danny is saying......i was gping off the diy's for shimming and carb piolet tuning aswell as snorkal removal diy.....and all the comments written in them

gonna leave the needles atm and see what happens with the new filter but adjusted idle screws

btw the bike felt hotter way quicker with the new filter in......unless it was just my imagination 🤔
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Old July 13th, 2019, 09:35 PM   #10
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If you make a change and the bike runs worse and then you put it back to how it was and it runs perfectly.......................Hmm? There can really only be one logical conclusion to what has made the difference
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Old July 13th, 2019, 11:08 PM   #11
Seirra117th
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lol lets try this way.......

1. was the AFR right with the old filter? because there was no signs of dropping below idle or hanging rpm after blipping the throttle.

2. why with the new filters increased air flow during idle.......making it leaner......does it get the symptom dropping below idle after a blip.......which i thought means the pilot circuit is now too rich???
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Old July 13th, 2019, 11:58 PM   #12
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Quote:
Originally Posted by Seirra117th View Post
lol lets try this way.......

1. was the AFR right with the old filter? because there was no signs of dropping below idle or hanging rpm after blipping the throttle.

2. why with the new filters increased air flow during idle.......making it leaner......does it get the symptom dropping below idle after a blip.......which i thought means the pilot circuit is now too rich???
1. Yes, AFR was right with original filter because bike idled properly.

2. Blipping throttle with new filter gives increased air flow but now not enough
fuel to maintain correct AFR so this could be a symptom of running lean not rich.
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Old July 14th, 2019, 12:45 AM   #13
Seirra117th
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so this is where im getting confused.......i install the new filter......turn both pilot screw in 1/4 of the turn to match......

THIS IS QUOTED BUT COULDNT WORK OUT HOW TO LINK IT
Now blip the throttle. Nothing crazy, just rev it to 2,500 RPM or so and let go of the throttle. Does the throttle immediately drop to idle?

If not:*

If the throttle hangs -*The idle circuit is still too lean. Loosen the screw down a little more

If the throttle drops below idle and takes a moment to return -*The idle circuit is too rich. Tighten the screw a little bit.

Then repeat the process until the idle is restored damn near instantly after you blip the throttle. I try to err on the side of 'rich' as this will help the bike warm up a little quicker and isn't going to REALLY affect fuel economy or anything in the end.

FROM VEX'S DIY ON Accessing and adjusting idle mixture screws

after starting......it took little choke to idle steady.......had to adjust idle level back too 1350 but doesnt hang or drop after blipping.

so why did making pilot circuit a tad leaner heap with a better less restrictive flowing filter.

VEX said that symptom was too rich pilot so i went with that solution.......yet id think the filter would have made the AFR leaner.
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Old July 14th, 2019, 12:45 AM   #14
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still confused as........
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Old July 14th, 2019, 12:46 AM   #15
Seirra117th
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Quote:
Originally Posted by DannoXYZ View Post
Try 3rd test with no filter.
Also look for spots where snails may have snuck into your intake.
btw found no snail's not in this beast of a machine anyway
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Old July 14th, 2019, 03:18 PM   #16
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Most likely in stock configuration, your clogged carbs were barely able to keep up with flow. Add tiny bit extra and they can't keep up. You need to take apart carbs down to individual jets removed from emulsion tube. Each and every bleed hole in jets and emulsion tube needs to be physically flossed out guitar wire of matching diameter. You'll find that spits out little plastic plug on inside. I also drip dye down centre of jet & emulsion-tube to verify each bleed-hole "bleeds" properly (Kool-aid or fruit-punch mix works well). Also clean out idle and transfer ports in carb venturi with wire. Then soda-blast every hole and circuit to clean out scrapings.


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Old July 14th, 2019, 04:35 PM   #17
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Over-oiled the filter is my guess.

Doesn't take much to create a problem. I've done it.
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Old July 26th, 2019, 10:06 PM   #18
Seirra117th
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Wink

would anyone find that i had the jet needles on the wrong sides?.........vw and da left and vu on the right ooops........just serviced float height......cant afford the clean danny mentioned but will try and service all parts of the carbs while rebuilding

jets are clean as for the 'secret passages' good thing i play guitar
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