Jetting/Needle height adjustment question ninja ex250

[ieathonda]

Ive got a ninja ex250 2005 that i bought a few weeks ago. Has a muzzy slip on exhaust. Did an airbox mod a few days ago and thought i should be good with a few #4 shims under the needle. Well im at 4 shims now and mid range still is lacking. I will be ordering a factory pro jet kit with adjustable needles sometime this week but wanted to see if I could get a few answers before it comes in.

Idles great. blipping the throttle, the rpm's climb and drop instantly, no hang or hiccup of any sort.

at WOT from first gear, accelerates hard until about 4k rpm. 4k rpm - 8k rpm feels like ive hit a wall. It just steadily climbs until about 8k rpm and the bike comes to life and shoots off. Having the throttle half open through the 4k-8k rpm range feels as if it has better acceleration than WOT.

After 8k rpm the bike pulls hard to redline with no issues.

Im unsure of whether it is running lean or rich, seems a little bit hard to tell since ive never worked on carbs before. I will pull the plugs soon and try to get a better reading that way.

In your own opinion, what do you feel is causing the mid range stumble that im getting? its taking most of the fun out or accelerating

[Ninjinsky]

I take it you mean it is worse than stock?
These engines don't deliver much until 7-8k after which they take off.
It's a bit like a 2 stroke power band
Below that cracking it open gets you a deeper noise but not a rapid increase in forward motion

[ieathonda]

Originally Posted by Ninjinsky

I take it you mean it is worse than stock?
These engines don't deliver much until 7-8k after which they take off.
It's a bit like a 2 stroke power band
Below that cracking it open gets you a deeper noise but not a rapid increase in forward motion

Yes significantly worse. When it was stock (with muzzy) there was a slight delay from 6-7k rpm. Now it feels as if that "delay" or flat spot has widened to 4k-8k rpm. When i mean flat spot, im talking 4-5 full seconds for it to get through 4-8k rpm.

I live in Houston which is about 18 meters above sea level.

Would something as simple as an airbox mod cause such a dramatic decrease in performance?

It ran alot worse with no shims under the needle and has gotten a good amount better but nowhere near how it was performing stock.

Also, is there a point in which raising the needle provides little to no performance gain? I can try another washer but Ive read from Factory Pro's website that if 4 washers have to be added then you should go up a jet size.

The top end runs great right now and im unsure of whether it could be better but would going up a size hurt?

[Ninjinsky]

You might need to look at doing something more radical like
http://store.58cycle.com/product_p/dynojet%20ex250.htm
I have not modified mine beyond a couple of washers under the needle but others on here who have modified their bikes will chime in with their experience I am sure, (I am in the UK so it is a a while yet before the California ninjetters get home from work

[Singh2jz]

Yes, you will have to rejet. Check this site out..http://faq.ninja250.org/wiki/Muzzy_Exhaust

[Ninjinsky]

Originally Posted by Singh2jz

Yes, you will have to rejet. Check this site out..http://faq.ninja250.org/wiki/Muzzy_Exhaust

Indeed there is a complex relay of responsibility as you open the throttle.
Here is a diagram of the changeovers between various sub systems in the carb as you open the throttle.
nb This is throttle opening not RPM

http://www.arcticchat.com/forum/atta...b_circuits.jpg

[ieathonda]

Yes I have been reading the ninja250 wiki extensively. I havent worked on carbs before but have years of experience on working on automobiles and manually adjusting carbs is definitely an art in itself. I thought it was odd to have almost 4 washers under the needle and still have it running bad but I suppose going up on a jet size and retesting with stock needle settings will yield me with a change in performance.

I will definitely have to ride it, get it warmed up and check the plugs.

[Singh2jz]

Originally Posted by ieathonda

Yes I have been reading the ninja250 wiki extensively. I havent worked on carbs before but have years of experience on working on automobiles and manually adjusting carbs is definitely an art in itself. I thought it was odd to have almost 4 washers under the needle and still have it running bad but I suppose going up on a jet size and retesting with stock needle settings will yield me with a change in performance.

I will definitely have to ride it, get it warmed up and check the plugs.

Aight well, good luck! Keep us updated.

Oh, and how did the PO ride the bike without adjusting the air/fuel ratio?

[ieathonda]

Originally Posted by Singh2jz

Aight well, good luck! Keep us updated.

Oh, and how did the PO ride the bike without adjusting the air/fuel ratio?

PO?

The bike starts with no choke and idles fantastic. low rpm feels normal until the midrange stumbles when accelerating. at highway speeds it pulls a little less than it used to but has no problem cruising at 75-80. i also noticed that the bike would only hit 95 and hit the rev limiter whereas before 105-110 was a piece of cake. there was some crazy headwind though when i tried that out.

[Singh2jz]

Originally Posted by ieathonda

PO?

The bike starts with no choke and idles fantastic. low rpm feels normal until the midrange stumbles when accelerating. at highway speeds it pulls a little less than it used to but has no problem cruising at 75-80. i also noticed that the bike would only hit 95 and hit the rev limiter whereas before 105-110 was a piece of cake. there was some crazy headwind though when i tried that out.

Previous Owner.

That is torture in disguise! I thought it would've just ran hella rough throughout the whole rev range lol. I'm still new in all things carbs, so bear with me haha

[FvnnyL3tt3r1ng]

You have to change the main jets as well you can't just shim the needle. Yeah they're for the high-range but it still effects the whole spectrum.

[ieathonda]

Well the PO only had the muzzy, seems like its not the full exhaust since I see some janky welds on the pipe midsection. But it did have a stumble midrange but wasn't as bad as it is now.

I'm going to stop riding the bike so I can avoid any potential catastrophe with the lean condition. I am also going to call factory pro tommorow and see what their recommended setting would be and go from there...

Would it be a good idea to buy a carb rebuild kit? If so, would I need two? One for each carb? Or is it even necessary to buy a rebuild kit? I would only think the gaskets/orings would need servicing but you guys probably know this bike better than I do..

Also it only has 11k miles. I'm going to check valve lash and sync the carbs since ill have everything out. Is it normal to do all this service only after 11k?

[Ninjinsky]

Originally Posted by ieathonda

Would it be a good idea to buy a carb rebuild kit? If so, would I need two? One for each carb? Or is it even necessary to buy a rebuild kit? I would only think the gaskets/orings would need servicing but you guys probably know this bike better than I do..

The float bowl gaskets and the needle valves are the bits that tend to need replacing. When you dismantle the carbs be extra careful with the diaphragms, they are expensive new and hard to find s/hand in good shape.

Regarding pro kits like the k&n their stuff will be dyno'd but of course that is for their filters only.
Once you start making your own mods you are in the woods without test equipment for rejetting correctly. Which is of course why you come here, to find what worked for others.
Jet needles alone are a science, eg here is an article on the KDX200 needles:
http://www.dirtrider.net/justkdx/jetneedles.html
(note that in his diagram the needle height starts to run out of influence over half throttle )
My inclination would be to start with standard then proceed with proprietary or well established and documented mods that are known to work right.

[ninjunk]

nobody (including the people that sell 'jet kits') can tune your bike over the phone or internet.

that said, mine has 40 pilots and 105 mains and it runs good stock, i've sanded down the needles a tiny bit to fatten up the midrange. I think the 40 pilot and 105 main 'corrects' the too-lean condition that these bikes are stuck with from the factory in order to pass emissions.

With your mods i'd be guessing at least 110 or 115 mains and maybe a 45 pilot. I'd probably buy 110, 112.5 and 115 mains, and 42.5 and 45 pilots, and practice getting really good at removing the airbox, haha.

the pilot jet is going to have the biggest impact over your midrange, if you have your pilot and air bleed screw tuned correctly, you shouldn't need more than 2 shims on the needles, the progression of fuel delivery probably wont change much.

the airbox is a fairly sophisticated resonator that ensures consistent pressure is delivered to the carbs at all times. 9 times out of 10 you will hurt your midrange and lowend by molesting the airbox. You probably will loose some midrange as well with the exhaust. The airbox and exhaust mods are for pure top end, but mostly so the bike will be louder and you will think you are going faster. Kawasaki has done a pretty good job tuning this bike from the factory, 25 hp from 250cc's is no joke.

[ieathonda]

Thanks for the help so far guys. I wanted to call FP to get an "approximate" jet sizing so I can kind of guess and check for the right sizes.

Another thing I wanted to touch base on, are the factory pro needles the cream of the corn or are they just a fancy unnecessary needed item? I know their website says they have been engineered specifically for applications like mine and that they're steel, but do they make such a dramatic difference that justifies the cost of buying the whole kit from them? I know they are height adjustable which is nice as well but will I be better off buying from jets r us?

[ninjunk]

eh, i dunno.. .never bought from them. as far as i'm concerned a needle is a needle. its gotta be the right size that's about it.

like i said, i don't trust anyone who claims to be able to tune my bike over the phone or internet. how do they know their needle is a better fit for your bike?

i take the needle, chuck it in a drill and use some 400, 600 grit sandpaper to slim it down a little in the areas that need more fuel. slim it down near the bottom for upper-midrange and slim it down near the top for lower-midrange. This is getting into some pros-only type stuff here, you should be good using the stock needle and adjusting pilot and air bleed accordingly.

[FvnnyL3tt3r1ng]

I'm not sure how the FP needles compare to stock but I know my bike ran wonderfully the whole time I owned it after I installed them.... It is a very precise taper mind you....

You start tuning the bike from the top end. If your bike is starting cold w/ no "choke" then I'd probably start leaning it a little bit from where it's at. Once you have to use the choke you're in the ballpark of the correct mains. I ran 110s at sea level.

I forgot to ask you what you meant by slip on muzzy? I don't think they make a slip on. Stock pipes go to either side of the bike, if the header is a 2-1 and goes to the right side of the bike it's the full exhaust....

How long are you riding the bike when you go out to test it anyways? The bike might not be getting warmed up enough if you're too quick. I know it's cold in Texas so it might be necessary to ride the bike for a while to make sure it's fully warmed up.

[ieathonda]

Well the muzzy is welded and has different diameter pipes through the midsection from the Mani to the exhaust. Ive worked on cars for a few years and it definitely looks like it was rigged up lol.

Yeah I thought it was odd that the bike started fine without choke. I may have to look into that more

[Singh2jz]

Do you mind taking a picture of hat you're talking about? If it's a ghetto header then that could be contributing to the problem.

[ieathonda]

Yeah ill snap a picture when I get a chance. Its at a friends right now while I clean up the garage

[FvnnyL3tt3r1ng]

Just for reference I ran pods + stock pipes with my factory pros and after I put on my muzzy full exhaust the settings for the jetting didn't need to be changed.
Your valve clearances are also a factor in your final tune so if you have a service interval coming up doing the clearances would be well advised before starting on the jetting.

[ieathonda]

Thanks for the input. I have dozen plenty of valve lash adjustments on cars so I dont feel it will be too difficult for me to do so on the ninja. I will probably need a tad bit of time to familiarize myself with the orientation of the cams before it will become second nature

I also found the FP kit on ebay for 15 dollars cheaper with buck since shipping which is a plus in my book. I decided it would be the best bang for my buck since it includes an array of parts

[Ninjinsky]

Originally Posted by ieathonda

Thanks for the input. I have dozen plenty of valve lash adjustments on cars so I dont feel it will be too difficult for me to do so on the ninja. I will probably need a tad bit of time to familiarize myself with the orientation of the cams before it will become second nature

We will see how you get on setting the exhaust clearances, its like keyhole surgery lol. Looks easy till you try to get at them. (There are special tools available though)

[ieathonda]

Originally Posted by Ninjinsky

We will see how you get on setting the exhaust clearances, its like keyhole surgery lol. Looks easy till you try to get at them. (There are special tools available though)

I do have available to me a valve adjustment tool and a myriad of feeler gauges. I already feel as if getting my hands in such a small space will be the tricky part. Im just glad I dont have 16 valves to adjust

[FvnnyL3tt3r1ng]

I have the Kawasaki valve adjustment tool if you want to buy it off of me. I no longer have a ninja.

[choneofakind]

**** justin, if OP doesn't want it, how much are you asking?

[FvnnyL3tt3r1ng]

$25 shipped

[choneofakind]

If OP doesn't want it, consider it sold and PM me for paypal address/shipping address info.

[ieathonda]

So i spent the evening after work to take apart the bike and prepare for valve lash adjustment.. Im gonna need that tool off of you

Exhaust rocker arms have a really funky angle to them. intake isnt too bad but there is definitely no clearance for me to use the tool I have.

also, the closest i could find to spec on my feeler gauges for the exhaust and intake were .004in and .003in respectively. exhaust seemed like it tightened up quite a bit.. even the .003in feeler wouldnt slide in. just wanted to put that out there to see if anyone else can relate.. once again, the bike has nearly 11500 miles on it now.

BTW, I took apart the lower fairing and can confirm indeed that it is a muzzy full exhaust.. at a glance it looked as if the welds were janky but i suppose that is not the case..

[choneofakind]

pro tip, a deep well 1/4" drive socket (8mm IIRC?) and a long skinny eyeglasses screwdriver also works. That's how I've adjusted the valves before now. But since you're getting his tool, that's how I'll continue to do so.

[ieathonda]

Originally Posted by choneofakind

pro tip, a deep well 1/4" drive socket (8mm IIRC?) and a long skinny eyeglasses screwdriver also works. That's how I've adjusted the valves before now. But since you're getting his tool, that's how I'll continue to do so.

I was thinking of using the same method.. but I will try out a proprietary tool this time and see how much easier it can be.. after im done adjusting the vales, ill pm you

[Singh2jz]

Originally Posted by ieathonda

after im done adjusting the vales, ill pm you

and then he can pm me after he's done..haha

[ieathonda]

So my sister wanted to take my bike out yesterday. She got scared halfway doing a turn on the cul de sac and hammered the curb. Crooked steering, cracked dashboard, destroyed front fairing and right turn signal, half the brake lever is intact, muzzy exhaust scratched to hell with the addition of grass everywhere, headlight bracket bent to crap.

Fixed most of it last night and bought all the parts to street fighter it last night as well! Thankfully she was ok (yes she has a license and took the msg course) with only a messed up hand from no gloves and a bruised chest.

So I got really impatient and went ahead and did the 9mm deep socket and eyeglass screwdriver method to adjust the valves. Went fantastic and sounds great.

Waiting for tommorow to come to install the main jets. I'll be scouting out for the brown truck all day. Pretty excited to get the bike running as it should.

BTW that tool is available to whoever can get it first from out buddy funnylettering!

[ieathonda]

small update: got the main jets and pilots installed, clip on the needle is set halfway, floats set at 17mm and everything cleaned out. I just need to get the airbox back in and i can do some testing tonight.

[ieathonda]

So i changed out the mains to 112, needle clip position is one below the middle, pilots at 40 and mixture screws set out at 2 1/4 turns.

Installed a KN drop in filter as well.

Pulls DRAMATICALLY better mid/top rpm range! had to tune the mixture screws a bit cause i had them at 3 and when blipping the throttle it would drop down below idle and barely get back up.

The only problem is that from a stop in first gear, if i dont give it enough gas itll die. and there was one instance where i was sitting at a red light and the engine died as well. i did mess with the idle screw ( black knob pointing out to the side ) a bit. its kind of hard to tell my idle rpm because i have a trail tech vapor and the rpm's are jumping all over the place.

what would be the main cause of the bogging from a stop? Before the 40 pilots, the stock pilots worked great for off the line. should I just switch them back and see what happens?

Thanks for your input

[ieathonda]

Also, for those of you with a trail tech vapor...

I got erratic readings due to no resistor. I changed the ppr to 2 and now the rpm is steady. I am unsure of how accurate it is but it is definitely way more precise and not jumpy like it was on 1 ppr.

As for the jetting, I will change the pilot jet back to a 35 since i didnt have these low speed problems before the pilot jet change. I will post back on here and let you guys know of the results.

[ieathonda]

Spoke too soon on the vapor. Rpms are still erratic. Will be purchasing a 600ohm 1/4watt resistor at the local electronic parts outlet.

Didn't get a chance to reinstall the stock pilots. Rode it around town just to see how it would run. Runs better cold than warmed up so I'm suspecting its running rich down low. I'll get a chance to mess with it hopefully this weekend.

[FvnnyL3tt3r1ng]

The resistor for the tach is a good buy. I heat shrunk mine. If they don't sell the resistor in your size you can always solder them in parallel to obtain the proper (ohm) resistance. My vapor tech was acting up until I wired it into the bike battery. No more problems after that.

[ieathonda]

They'll definitely have it at the place I go to, not your run of the mill radioshack! Got plenty of heat shrink and a soldering iron at hand. Will be picking up the resistor tommorow.

When you say you wired the tach up to the battery, do you mean that you wired the tach wire to it? Or the power wires? And do you have the resistor installed as well?

[ieathonda]

got a few resistors together with an electrical engineer of mine. will be installing shortly.

I rode the bike last night for an hour. When cold, getting off the line in first is smooth and predictable. After the bike warmed up, i have to slowly ease onto the throttle for a few seconds and if it doesnt die, itll shoot up to 6-7k rpm instead and i have to let off a little before engaging the clutch in first gear and take off. Very bothersome and definitely running rich. Cant wait to tear it all apart again!