Keihin OEM vs Factory Pro jet sizes

[kkim]

again, your call, but I repeat... do only one change at a time and test after each change you make. keep notes in a small notebook. your memory is not as good as you remember it to be.

Personally, I always try to work from what's easiest to hardest, but only because I'm lazy and want to do only what's absolutely minimally needed to remedy a problem. Sometimes that's the smart thing to do, sometimes not. This is why this is called fine tuning and is such a PITA.

[headshrink]

Boy, you aren't kidding about the memory. I have been logging every detail, and have found that with each attempt, my descriptions can even change..... but all together, when I look at it big picture, it seems to come together a little bit. I just adjusted screws to 3.5 turns out, synced, and am on my way to work (commute will be the test).... will report back.

[headshrink]

Here is the verdict from post#42 (above): The surge/stutter is virtually gone now. There MAY be traces still, but it is difficult to discern over rode vibrations. It is significantly improved though. I need to continue to test, but there MAY be a slight flight spot on the higher end of the midrange that wasn't there before I turned the screws that last .5 turn. I could be wrong, but this is my initial impression. Also, I took the long way home today, and the weather is warming up (high 80s) and my engine was running ~180 to 210 degrees, vs. 145-175 this past month. I noticed by the time I was almost home, at a light, that it was idling ~200ish RPM higher than I had it set at.
How do you read this?
I was thinking about first removing one washer to put the needles at clip position 3.5, in hopes of fixing that slight flat spot.
If all goes well, and if that doesn't sig affect the stuttering, trying to turn the screws out 1/4 turn (after that I believe I have to go to the new pilot jets).
Am I starting to get it down at least.... on the right track?

[kkim]

Ride the bike again and see if the idle goes back up to the 200 rpm higher that you saw. If it does, readjust the idle to it's proper speed, once the bike is completely warmed up, then test the bike again to see if that changes anything.

After that, make a guess as to whether you're too rich or too lean in that midrange flat spot and test accordingly.

This is the PITA part of fine tuning... you makes your best guess, act on it and hope you're right.

all things considered, is your bike running better now than when you started before the jet kit?

[headshrink]

Originally Posted by kkim

All things considered, is your bike running better now than when you started before the jet kit?

Heck yeah!!!

Honestly though, I was really surprised I was advised to go down in size on the main, yet had to richen the crap out of the low and mid..... I expected the main would need to be richened too, but since I didn't really try anything above #98, who knows how it would handle. I just know the overal ride is better thus far..... so I'm not complaining. I would HATE to pull those carbs again.

[headshrink]

I have found that my idle will creep up a tiny bit after running a while (not just initial warm-up). The 1/4 throttle surge remains, but I haven't been able to duplicate the midrange flatspot. You are not kidding about it being a PITA, I feel like I'm getting mixed signals around low end.... it is rich-lean. I guess my bike really is a she.

[kkim]

Originally Posted by headshrink

I have found that my idle will creep up a tiny bit after running a while (not just initial warmu-up). The 1/4 throttle surge remains, but I haven't been able to duplicate the midrange flatspot. You are not kidding about it being a PITA, I feel like I'm getting mixed signals around low end.... it is rich-lean. I guess my bike really is a she.

Idle speed should be set after the bike is fully warmed up (10-15 minutes of riding).

Try going one clip notch richer and see if that helps the 1/4 throttle surge.

[headshrink]

That is exactly what I was thinking.... this is good, I AM catching on
Thanks Kelly.

[headshrink]

Here is the frustrating update since last time:

Attempt#7
Rather than go up an entire clip position, I tried just one washer to make a little smaller change. That put me in the neighborhood of clip position 4.5-ish.

This did sig. improve the surge, but there was still a slight surge
I was having that idle creep

Attempt#8
Turned the mixture screws in 1/4 turn (3 1/4 total out)
This improved idle (steadier, or returned to home base after riding a while)
There was still a slight surge at 1/4 throttle, but I was really just fixing the idle creep here and didn't expect an improvement in the surge issue on this attempt.

Attempt#9
Added 1 ea. washer (clip position somewhere between 4.5 and 5).
Idle didn't seem to get any worse, but this wasn't what I was paying close attention to.
The surge improved again, although I believe I was able to duplicate a slight surge here and there...
My biggest complaint though is it got harder to take off from a light. I believe it bogged a couple times.... which makes me think it is too rich down there. Over all it handled better back at attempt #8, although the surging was better (not gone) at #9

So.... should I pull that last washer out, turn the mixture in 1/4 turn, do something more drastic? I'm trying to read your mind and anticipate you'll say to turn in the mixture screws.... am I close?

[kkim]

what mains are you running?

[headshrink]

Originally Posted by kkim

what mains are you running?

Still running #95.

[kkim]

go up one step to... #98 is it? and start over with the clip in the 3rd position. this is why I suggested starting off w/ the 98s to begin with.

[headshrink]

Hmmmm. I could have sworn you said start with #95, which confused me.... that is why I started there. Marc at FP said to start with 2 under stock, but that was a little too radical for me. Maybe we got our wires crossed at the begining. I know you have a ton of people throwing these questions at you.

I will do as you suggest, and start over again at #98 stock mains. At least I am getting a little quicker at this. While I have the carbs out, do you suggest I throw in the included FP pilot jets since it is included? This would be the easiest time to put them in.

[kkim]

one change at a time so you can see what each does. 98 mains, clip in the 3rd position, stock pilots. eventually, you may need to move the clip down to position #4 if the bike runs a bit lean in the midrange.

I'm pretty sure I've never recommended the 95s... sorry, if I did.

[headshrink]

Yeah, I think you are right...I just checked the begining of the thread. I have NO IDEA why I thought that. It must have been one of those points we were slightly on a different page and I missinterpretted what you where actually saying. I'ts all good. Thanks for hanging in there with me!

[g21-30]

Bob,

Check this thread and match what he did (except for the Area P exhaust system):

http://www.ninjette.org/forums/showthread.php?t=45478

[headshrink]

I would expect the Absence of the Area P would be too significant to match exactly, but who knows.... maybe I'll have a paradigm shift and get one one day anyways.

[g21-30]

Without the Area P and the .040 Pilot Jet, you would match my bike.

[headshrink]

Originally Posted by g21-30

Without the Area P and the .040 Pilot Jet, you would match my bike.

Maybe there is something I am not understanding....

When I hear, "with out the XYZ," I hear every thing that makes out bikes different..... so how can that make them equal?

[headshrink]

I returned to "default" position as mentioned before
#98
3rd clip
2 1/2 turns out

Top pulled a little stronger.
Mid wasn't as smooth throughout as I would like and even had some surge in a spot.
Low was often weak and surged


Next adjustment:
I then raised the needles with 2 washers (ea). I believe that puts me in the neighborhood of 4th position. I prefer to use washers because I don't damage anything moving the clip around with each attempt.

High still felt good, and mid improved, but there may have been some slight stutter here and there at cruising throttle. Low sucked. The surging was still there, although not as bad. Unless I finessed it just right, it would bog for a second.... like it would move forward lethargically, take a breath, then start jogging. I know the language sounds like I am describing a rich situation on the mixture, but it reminded me more when the bike was new, before shimming fixed it.

So.... attempting to read your mind again, I think you will tell me to raise the needles one more time (maybe only one washer ea.), test it without worrying too much about the low, but noticing how it was affected, then move on to the mixture screws once the mid is smoother.... How close am I to being in your head?

[kkim]

I know this will be subjective, but was the mid stronger, weaker or the same now than when you had the 95s in there?

You can do a couple of things at this point... 1) add more washer/s, but only if the mids felt weaker overall than before, 2) retune the mixture screws a bit richer or 3) install the 40 pilots that came with the jet kit. (did yours come with extra pilot jets?)

on adding more washers... the general feeling is that if you get down towards the extreme (#1 or 5) clip positions, you either go up or down on the main jet accordingly.

with regards to adjusting the mixture screws, I'd do that as that's the easiest to do right now and it seems you're after fine tuning a slight stutter out at cruising speeds.

or... you can install a one step richer pilot jet and retune the mid and low speed circuits.



as far as reading my mind... good luck with that. I drive the wife crazy when she does things thinking she knows what I would do but end up doing the exact opposite of what I'd actually do. Some real good, heated "discussions" ultimately ensue.

[headshrink]

I see what you mean be this being an art. Although I keep detailed records, my descriptions are pretty subjective too, and even then it is difficult to interpret my notes, as I have to also rely on memory to compare "good" with "good". I can't be certain the mid is stronger now, but it may be.... not by a lot though. Yes, my kit did come with the extra pilot jets too. One thing I do know though for certain.... when I was using the #95 and kept upping the needles and screws, it got way lively down low and mid, even though there was some stutter.

I'll pay closer attention to the mid on my way home today... not sure you about that mid.

I know I get on others for trying to read minds, but I think you just sent me a challenge

[kkim]

Originally Posted by headshrink

I know I get on others for trying to read minds, but I think you just sent me a challenge

I know the wife would agree that I should go see a psychiatrist.

[g21-30]

Originally Posted by g21-30

Without the Area P and the .040 Pilot Jet, you would match my bike.

I should have said "Without ...., your carburetion would match my bike!" Your OEM CDI will never match the '88-94 CDI in performance.

[g21-30]

Originally Posted by kkim

I know the wife would agree that I should go see a psychiatrist.

No need, kkim! You're already conversing with one (headshrink).

[headshrink]

Originally Posted by g21-30

No need, kkim! You're already conversing with one (headshrink).

I never claimed to be any good at it though. I just say, "stop that!"

[headshrink]

Kelly - Per you post #61, I opted to raise the needles with 2 washers (approx 4th clip). Mains still at #98, and screws still at 2.5 out.
Results = Mid was a little smoother, w/ some surging at low/cruise throttle. Low had both hesitation off the line, and some stuttering.

I then tried to work out the surging by turning the screws out another 1/2 turn (3 out total). Results = improved surging, although still present... primarily at low/cruise throttle. Of the line still needed some coaxing due to hesitation.

Then, I tried another 1/4 turn out (3 1/4 total).
Results = Even MORE hesitation off the line, and idle would drop before finding its spot (hunting I guess). I recognized this as signs that it was too rich. What stumps me though as there was STILL some stutter/surging.

Then I decided to put the mixture back to where it was before I started turning it up, and add another washer to the needles. Although this is changing 2 things at once, with my data, it was really only changing one, since I was essentially going back in time and raising the needles instead of mixtures.... So I did add another washer (total = 3 and ~4.5 clip). When I went to reset the mixture to 2.5, the bike didn't like it (it was running). I adjusted idle too, but it still wasn't happy. I added 1/4 turn, and it idled much more smoothly. So in summery that put me at #98 mains, 4.5 clip, 2 3/4 turns out with stock pilots.
Results = Both the lows and mid felt a little stronger.
BUT, and this is driving me crazy, there are STILL hints of stutter in the low end, & hesitation off the line, although a little bit less of both.

Since I am getting so high on my needle, I gather going up a main is one option, but I would hate to be soooo close, only to redo everything else if I can just try one more washer for ~clip position 5.

Could there be another cause of the stuttering, since it seems so consistent, even though the amount changes? In doing google searches, I read and saw some videos on making adjustments to the accelerator pump on the carb..... but since I have seen NO reference to this here, in the SM, or any other Ninja250 source, I assume ours doesn't have an acc. pump on the carb.... am I right? As far as I can tell, all the vacuum tubes are connected and in good condition, so there are no obvious leaks there... although if I HAD to pick a weak point, it would be where I added the ports for syncing the carbs. Again, no obvious leaks, but the ports are only sealed by those little vacc caps. Hopefully they are sufficient, since that is what they are designed for.

So, unless you think I am going in the wrong direction, I'm going to see what that one last washer does next. Since I ended up turning the mixture down, I'm also going to wait on the FP pilot jets.

Your thoughts?

[kkim]

Sure, try the extra washer. Interesting, isn't it, how such a small adjustment to the carbs can have such a pronounced affect on the engine running characteristics?

when was the last time the spark plugs were changed? sounds like you might be having another issue.

You can try continuing down the thought process you're on... sounds like you have a great understanding now of how the jets interrelate, but if the plugs have been in there a long time, try changing them. IIRC, you have a lot of miles on your bike. They cost less than $10 for a set. May save you some headaches.

[headshrink]

Originally Posted by kkim

Sure, try the extra washer. Interesting, isn't it, how such a small adjustment to the carbs can have such a pronounced affect on the engine running characteristics?

when was the last time the spark plugs were changed? sounds like you might be having another issue.

You can try continuing down the thought process you're on... sounds like you have a great understanding now of how the jets interrelate, but if the plugs have been in there a long time, try changing them. IIRC, you have a lot of miles on your bike. They cost less than $10 for a set. May save you some headaches.

Thanks for the compliment... I still feel like a baby though in my mechanical understanding. I'm probably bordering on that "a little bit of knowledge is dangerous" part.... well, maybe starting to move out of that a little, since I am getting a little more conservative.

Plugs were changed at 15K, which was only about 2.5K ago.

[kkim]

and they were the exact, recommended NGK plugs, correct, and not some fancy, schamzy plug?

if so, keep fine tuning the carbs till you're satisfied.

[headshrink]

Originally Posted by kkim

and they were the exact, recommended NGK plugs, correct, and not some fancy, schamzy plug?

if so, keep fine tuning the carbs till you're satisfied.

Yes, the exact plugs that are recommended in the SM. I might pick up a spare pair next time I'm at the store so I have them on hand. It wouldn't be a terrible idea to check my plugs just for looksies next time I have her naked.

[headshrink]

Results after adding another washer:
#98 main
3rd clip + 4 washers ea. (~5th clip)
2 3/4 turns out

Possibly the best mid-range performance to date.... more than I believed possible. The bike ALMOST feels like it wants to come out from under me.

I can't get a very good WOT top end test yet, as the PD is EVERYWHERE as they are currently trying to keep their jobs, and I got nailed 3 wks ago.

Low is still giving me trouble. There is still some hesitation off the line, and once it goes, it isn't flat or dead, but it's not very strong or as linear as it used to be. TBD on the stuttering/surging.

I was going to play with the mixture screws to see if I could work out the hesitation.... I was going to try both turning IN and OUT, but 1/4 turn + OR - shows up in idling behavior (hangs or hunts). So I don't have anything to work with there.

I pulled the plugs, and they looked a little on the dark/rich side, but I don't know how accurate that is since the plugs have been in there since my 15K and all the tunings, and re-tunings since....

I don't recall ANY hesitation OR surging problems before I got the jet kit. I was at 3 washers back then, but never tried 4. Still had the caps on the screws, and only other mod was (still is) yanked snorkel. I don't want to go back to that, since the new mid is awesome, but can't figure out that crazy low end. Any ideas what I can try next?

[kkim]

Bob, with the needle being effectively in the 5th position, you may want to up the mains one step and start the needle back at the 3rd clip position. It sounds to me like your bike needs more fuel and a larger main would supply that throughout the entire range, including the mixture circuit, where you seem to still be lean even with that needle at it's lowest position. ignore the black plugs for now.

if you don't want to up the mains, you could try to up the pilot jets one step to a #40 and see if that cures your stutter and smooths out your power curve.

whatever you do, I suggest a new set of plugs to 1) eliminate any possible problems being introduced by faulty plugs and 2) you can get better readings starting from a "clean" set of plugs.

it sounds like you're close... don't give up. I know it must be frustrating at this point, but you'll reap the benefits of your hard work soon and then you'll be as happy as a pig in poo.

[headshrink]

Well, since the image of a happy pig in poo brings a smile, and I would like to smile more, I will give that a try. The next main jet in my kit is a #100, so I'll put that in and zero everything else out. While I have the carbs out, should I throw in the #40 pilots at that time too, or wait to see if it is needed?

It strikes me as odd that the FP jet kit came with several mains smaller than stock, and only one bigger. I can't recall a single post anywhere where anyone settled with a main jet smaller than stock. Since I have a stock pipe though, I don't anticipate needing anthing larger than the #100 though..... Tomorrow (Mon.) I will start tuning attempt #16, at least I am getting quicker at tearing down and putting back together.

[kkim]

well, do you agree based on the indications you're getting that a larger main is the way to go?

if you are okay with possibly taking the carbs apart again to remove the #40s if you install them with the 100s, then by all means install the 40s with the new mains. Based on my experience, though, I like to change only one thing at a time to see how that one change affects the picture. when 2 things are changed, you aren't really sure which did what.

[headshrink]

Yes, I'm thinking the larger main probably is the right thing. Since this will add fuel across the board, and especially since I have backed my mixture screws down, the #40s might be over-kill.... you remind me of those professors that answers questions in a way that makes you talk it out yourself and end up answering your own question... You've done this before

OK, #100 main for tomorrow's agenda, stock pilot, 3rd clip, 2 turns out (or 2.5, I'll have to double check), test and observe.

[kkim]

not trying to lead you to any set way of thinking, but more trying to get you to see that you know a lot more than you think you do. there's no right way to go about fine tuning the carbs and what I suggest may be totally wrong. there are set principles involved and you and I are pretty much on the same wavelength of what affects what.

I'm simply throwing out my thoughts to you... you're the one there that needs to evaluate if what I suggest jives with how you understand jetting to work. if you decide to go a different route and prove my thinking wrong, I won't be hurt... the end result we're both trying to work towards is getting your jetting spot on. When that happens, we'll both be happy no matter the route we took to get there.

one last thought that just popped into my head. try plugging the kleen port to the head and see if that helps with the stutter. the kleen system may be injecting air into the exhaust and leaning the mixture at low throttle inputs.

I'd suggest trying this before rejetting again. simply disconnect the hose from the top of the cylinder head, cap the pipe on top of the head and plug the end of the hose that went to that port. costs you nothing and is completely and easily reversible if it doesn't improve the stutter.

[g21-30]

Bob,

Since FP recommends that the First step in CVS Carb tuning is to obtain the proper main jet, might I suggest that you go to the FP website and read the tuning technique section? I personally find it hard to believe that you need larger main jets when you are still running an OEM exhaust system!

[kkim]

Originally Posted by g21-30

Bob,

Since FP recommends that the First step in CVS Carb tuning is to obtain the proper main jet, might I suggest that you go to the FP website and read the tuning technique section? I personally find it hard to believe that you need larger main jets when you are still running an OEM exhaust system!

so do I, but aren't the symptoms he's seeing pointing in that direction?

[headshrink]

I didn't think about the kleen air system.... I think I will do the main jet anyways, just to satisfy the question of what will happen. That way, even if I go back to a #98, I'll have the peace of mind of knowing I have the right one. If things don't improve, or if stutter remains, I will certainly plug the system.

I did just have another thought to rule out though.... I drilled the slides way back when, and FP says you don't need to do that. Could this be having a neg affect, perhaps causing my hesitation?