Re-questioning #40 Pilot Jet...

[GiGs]

It's now summer and the bike hasn't 'changed' so jetting is still correct it seems.

Haven't pulled the plugs in a while to check but last time I did (after full throttle runs etc) they were golden brown...there is a picture around here.

When the throttle is blipped and it's still cold and the engine is still warming up or the engine is fully warmed up it's perfect. Has a very tourqey feel also...the only thing i'm just a tad un-happy about is take off.

When taking off from the lights there is just a small period where nothings really happening then bam off you go ! Doesn't really make much of a difference if I launch at a higher RPM either...

I remember running a #40 pilot jet at one stage with various mixture screw settings (not as lean as it is now though to be honest) and take off just felt absolutely perfect BUT it was definitely too rich (black plugs, popping and rpm drop/rise).


Bottom line : is there any way I can improve take-off since mixture settings (according to plugs last time I checked) say they are perfect ? Would you say it's possible to re-tune the carb to run properly with a #40 pilot ? Is there any real harm in running a tad rich ?

cheers

[Racer x]

you should be fine with a #40 pilot and maybe turn you Idle screws out a touch. See if that helps .Are you running a #38 now? Full system and pods?

[GiGs]

Yes full Yoshimura system, pod, clean air removed/plugged (112 main, 3rd clip, 1.8 turns out) - I'll give it a try again and see how it goes...btw no problems with the ICU so far old one was toast btw.

cheers

[JMcDonald]

For idle and low-throttle fueling, I wouldn't worry about being particularly lean or rich and would just tune the mixture screws for best performance.

[Nemesis]

Originally Posted by Racer x

you should be fine with a #40 pilot and maybe turn you Idle screws out a touch. See if that helps .

+1

[HKr1]

Originally Posted by GiGs

Yes full Yoshimura system, pod, clean air removed/plugged (112 main, 3rd clip, 1.8 turns out) -
cheers

For the mods mentioned.. 1.8 out sounds like the #40 is in there. Unless its not properly adjusted with the stock one.

Idle mixture setting tells you what pilot should be in there. More than 3 turns out, bigger pilot. Less than 1 turn out, smaller. Sounds like you need to re-do the idle mixture and see where ya stand. Atleast before you rip stuff back apart.

[Racer x]

Time to get a BRT- Tis. Advancing the timing some will help.

[GiGs]

Right, so I put a #40 pilot in today...before I started the bike with the new jets in I checked the plugs.

Plugs look like there *just* on the lean side...

Blipping the throttle at idle is spot on, no popping, take off is better (still not right though) but I tried a few launches at 3k - 4k and it seems it's way to rich (engine was flooding) - 1.7 turns out.

Seems like I need a larger main jet (i.e the process starts again) from the plug colour and a few other things...and it seems like the bottom end needs to be tuned.

It's almost blind guessing .....but i'm not giving up ! ..... (but I am also waiting until I get the AEM UEGO).

cheers guys

EDIT: pulled the plugs, #40 is just to rich ... from what the plugs were compared to how they were after the #40 was put in ... way to rich. Putting in 115 mains and working forward.

[JMcDonald]

If you are too rich, how would going to larger mains help?

Also, if launching at 3-4k gives rich indications, I'd imagine you need to lower your needles or even lean the mains, as you were most likely at higher throttle inputs and thus not in the realm of the pilot jet.

[GiGs]

To rich at idle ... prior to installing the #40 pilot the plugs were on the lean side, it was kind of 'hard' to push it to top speed.

I have tried different needle settings and pilot jets and idle mixture settings, the only thing left is the mains.

[JMcDonald]

You should get the mains down before messing with anything else. The main jets will affect everything else directly or indirectly, and you will be constantly starting over and over if you mess with all the bottom end and midrange stuff before changing mains.

Second, I am not sure if the plugs are a good way to determine idle mixture AFRs. If you just let it sit and idle, I am not sure if the plugs / combustion chamber will get hot enough to prevent buildup anyways. If you are doing any riding around, there are then other factors (main jet size, needle taper / position, and how much time you spend in each range on that trip) affecting the overall AFRs.

Also, like I mentioned above, in the lower ranges I would tune for performance rather than by apparent no-to-low-throttle AFRs (which, I think, are again not reliablly read by the plugs). Besides, in those ranges, the engine will tend to operate best with a good mixture anyways (including startup, warm-up times, as well as low-throttle performance).

But, really, if it is bogging at moderate throttle openings it sounds like you could either lower the needles a bit and possible in on the pilots a bit.

I have #40 pilots in and it seems to run well. I was consistently having to settle around 3-3.5 turns out with the #38 pilots, so I went ahead and put the #40s in and am now consistently around 1.25-1.5 turns out. Low-end seems about the same when I've had the mains and needles set pretty well.

Good luck!

[GiGs]

Sorry I should have been a bit more detailed, I haven't tried a 115 main yet but I believe I need richer mains (if not big deal, i'll put the 112 back in, pulled the carbs so many times today trying to make minor changes at a time).

I don't just let it sit and idle I take it for a 14K ride each time to test but can usually tell the difference (good or bad) before I get down the end of the road.

Also figured out that I was interpreting things wrong (thought rpm hang was rich till I read the FP paper again), I don't know how it ran with 1.8 on #38 pilot...at 3 turns out rpms were hanging !

I have since put a #40 in (againnn) and it's currently at 1.3 turns out and rpms are still hanging (i'll try 1.5 shortly, think that will be correct) but gradually getting better. 115 mains and needle on 2nd clip...

I'll keep testing and making minor changes, the FP paper also helps (when you read it slowly)......got my AEM UEGO, waiting on the SS extended bung to arrive.

cheers guys

[JMcDonald]

Getting better is always good! I am amid my own jetting woes, but also getting better .


How is it running up top with the 115 mains?

[GiGs]

Havn't had a chance to test it out properly as it's been on/off raining but I should hopefully be able to test it out tomorrow

I realize most choose 112, but I tried different clip positions (leaner and richer)...leaner was worse / richer did nothing and spark plug colour was still lean (I usually ride above 120km/h).

Currently, I am on #40 pilot, precisely 1.7 turns out, 115 main, 2nd clip.

1.5 was still lean and once I put it to 1.7 the problem went away, no popping and spark plug colour just from idle/rev is good (although this doesn't really prove much). One thing I noticed, changing from 38/40 a few times - when changing to #40 pilot the rpms at idle increase and need to be lowered.

Who knows, I still think a #40 might be to big (since every time I had it in previously and pulled the plug it was black) but after 3 turns out the #38 was still lean and far from close to getting better. So, not much you can do !

I'll see how it goes and report back, i'll probably tweak it more accurately (if it needs it) once I install the AEM UEGO

JMcDonald keep at it, you'll get it sorted

[JMcDonald]

Thanks. Where did you have the clips / shims with the 112 mains?
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[GiGs]

on 112 I had it on the 3rd clip (but also tried the 2nd and 4th)

[JMcDonald]

And no change in the midrange between those settings?

[GiGs]

leaner was worse and richer was the same

[JMcDonald]

Did you select your mains first by seeing which pulled the best in the top end? Because I'm having trouble following your steps to troubleshooting whether or not your pilot is too big :P .

[GiGs]

Yes, that and spark plug colour....when I was on 112 with a #38 pilot and I changed the needle from 3 to 4 there was no change in performance and the spark plug colour didn't change (was still the same).

I think I have been running a little lean for about 2,000KM's...not way to lean to the point of damaging anything (no metal balls on my spark plug ever).

I think i'm making things a bit confusing (sorry !) - it's been raining and I still haven't had a chance to test it but today is finally a sunny day ! I should be able to test properly how things are.

I made the assumption that a #40 is to rich for anyone since every time I have had a #40 in and pulled the plug afterwards it was black.

We shall see how it runs...if it's rich after I pull the plug and take off's flood the engine then I will finally settle on a #38 with mixture screws out more then 3 turns, since there is no #39.

I learnt more fuel doesn't = more power (unless you have a BRT Tis - I just can't justify the cost !).

[GiGs]

Ok so I finally tested it today but I can't exactly test it again (didn't happen to see the un-marked police car until it was to late....luckily the light went green and he was stuck in traffic !!).

I haven't pulled the plugs but I will shortly, I think it's to rich on the pilot because I could smell it and when coming down to hard stops at the lights once I stopped the idle slightly hung then dropped. I was WOT almost the whole test...the midrange feels sort of weak like theres a delay and there doesn't seem to be as much 'pull' in general.

Pulling the plugs now...will post back shortly...

EDIT:

ahhh, it's rich but not by too much (not as bad as previously - I have pictures previously to compare ) - I would love to try and test it a bit more but I really can't at the moment. I'm going to try and make the mid range leaner (i'll try going to 1 and also try 1.5) and see how that goes and maybe try and fix the idle 'bug'.

Here is a picture:

http://i745.photobucket.com/albums/x...g?t=1291877599

That was after WOT runs but 60km/h for about 800 meters (can't speed in an estate)

kkim said something about rolling off the throttle and if xxx happens it means it's a bit rich and if yyy happens it's a bit lean - i'll have to find it somewhere

[JMcDonald]

Originally Posted by GiGs

once I stopped the idle slightly hung then dropped. I was WOT almost the whole test...the midrange feels sort of weak like theres a delay and there doesn't seem to be as much 'pull' in general.

Sounds like a lean idle circuit, and possibly a rich midrange. I'd say the midrange was lean also, but having just enlarged the mains and subsequently seeing these conditions, that would be my guess. Did you move the needle when changing the jets?

How is the top-end after changing the jets?

I tried kkims tips but I couldn't tell any differences . Maybe they will help you. My problems might have been I was in a strong headwind (so I don't know if at any given moment the wind speed was 15 or 25mph), and the highway I was on tends to roll up and down. Between these two factors there might have simply not been enough time to see the changes before an external factor made obvious alterations to my speed.

[Racer x]

The 250 ninja engine has a natural flat spot from about 7000 rpm to 8500 rpm that just sorta flattens out the power curve till .
Look at some Dyno runs the power just sorta flattens out in the mid range. When I program the BRT-Tis .I start with the flat 35 deg timing the factory ignition uses .Then depending on compression .I will add timing between 6500 and 9000 rpm to hide that flat spot. If you run slightly rich jetting it will still be visible on the dyno. But you cant feel it on the road.

After you think you have everything sorted .Put in new plugs to test the settings. Once the plugs are used and go dark. The engine would have to run really really lean to go back to white again.

You should think about getting on a dyno. It will save a ton of time. What plugs are you running?

[GiGs]

Yes needle was moved from 3rd clip to 2nd clip in the main jet change (thought that due to the size of the mains going up i'd take down the midrange). I can play around with settings tomorrow...i'll take it easier this time

Racer x if your asking me, I use NGK CR8EIX plugs (I clean them after each test)...just bought a 88-94 CDI to and am waiting on the extended bung for the AEM UEGO So my theory is I saved a few hundred on a dyno by buying an AEM UEGO...I can't see any graphs yeah but big deal - they tune to an a/f ratio anyway which is what I plan to do.

I'm not trying to seem like I know everything either if it appears that way sorry

I appreciate all and any help ,

cheers guys

[GiGs]

Tried 2 things today:

Richening the mixture screws by (about) 5mm exactly on each side

Lower the clip on the needle from 2 to 1.5

Once it was all back together, idle was a bit weird so I thought whatever...got about 10m down the road and realized there was some big hesitation as soon as it got to 6k (or anywhere in the midrange). To lean !

Well, it's progress...2 was ok but felt a bit, so, hopefully 2.5 should fix that.

Extended bung for the wideband should be here in 2 sleeps

cheers guys

[Racer x]

This is what I am talking about .Look at the blue line( Session2 )That is a steady 42 deg timing setting . The same thing you get with a 88-94 ICU. Look at the power leveling off at the mid range on the dyno chart. . . Then look at the red line (Session 18).That little spike is all that is left of the power drop when you address the mid range power loss with timing. Fuel will not correct this.It took 16 pulls on the dyno just to work out the timing alone.This is all with a stock engine with stock carbs .and a Yoshi full system and 0990 filter.

[GiGs]

ahhh now I see, I was just about to ask for a dyno graph (can I ask what fuel you were using and what your a/f was or if you have any dyno sheets with that info ?).

I may consider a BRT TIS....(Racer x) can you program the cheaper BRT TIS with the timing you have or is it un-programmable ?

cheers

[Racer x]

Originally Posted by GiGs

ahhh now I see, I was just about to ask for a dyno graph (can I ask what fuel you were using and what your a/f was or if you have any dyno sheets with that info ?).

I may consider a BRT TIS....(Racer x) can you program the cheaper BRT TIS with the timing you have or is it un-programmable ?

cheers

It has been a long time for that. But I do remember I started with like 115 or 117 jets. I figured that was way rich. But I planned to adjust the jetting. As I increased the timing the air fuel ratio came into a sweet spot and the torqu made a huge jump. Yon cant adjust the less expensive unit

[GiGs]

Just an update...

Got my AEM UEGO all hooked up and the weather finally cleared for a little so I could take it for a test ride (it's summer and it has mostly been raining, do you believe it !?).

Idle - to lean (15 when idle'ing, 16-17 at lights)
Mid range - lean (13-15)
Main - to rich (10-11.2)

I'll post back and update my other thread once i'm actually done, also have pics of where I mounted O2 sensor bung etc

[headshrink]

Are you doing a welded or no-weld bung set-up?

[JMcDonald]

Originally Posted by GiGs

Idle - to lean (15 when idle'ing, 16-17 at lights)
Mid range - lean (13-15)
Main - to rich (10-11.2)

Thanks for those numbers!

If you could clarify two things for me, that would be great:

1) Specifically, to what RPM ranges are you referring when you say "idle, midrange, and main?" I ask because I only recently discovered that "top end" starts all the way at 7k, which is like a low highway cruising RPM, so to me it originally didn't seem appropriate to call it the "top end," heh. I always thought hte "midrange" was from like 5-10k, but FP says it's only 5-7k (which I now know to be much closer to the truth heh).

2) What is your setup again? Still the 112s, "1.5" needle position, and #40 pilot?

[GiGs]

I've had the bung welded onto the exhaust (pictures in my other thread)

Sure

Idle - 1-4k rpm
Mid - 5-7k rpm
Main - 7k> rpm

FP is correct

My current setup I have not tested, that set up (I think) with those numbers was 115 main, #40 pilot, 2.5 needle clip and 2.5 turns out. I think I can't really remember sorry, point was the main was to big so everything else is irrelevant.

One thing to note is that elevation and mods will change your jetting (my elevation is only like 40ft above sea level).

I'm currently on 112 main, #40 pilot, 3.5 needle clip and 2.8 turns out...idle seems perfect (was about 13.8/14 idling but rev'ing and stopping at the lights will be a bit different).

I haven't tested this, and i'm now basing 'correct' jetting based on A/F ratios which seems to have made a big improvement as apposed to guessing blindly and looking at plugs (which will get you close but not perfect if that's what your after).

I'll post up some numbers again when i'm done, right now the bike won't friggen start and my kill switch does nothing ahh !! I hate electrical problems !

cheers

[JMcDonald]

Yeah, that sounds like a really good way to do it, especially if you are able to datalog.

[GiGs]

It does have data logging capabilities (to a degree) but I haven't hooked any of that up because I can read it while i'm riding

Since you can only make small changes at a time (once you get the main jet correct ) i.e needle clip position or idle you either get it right or wrong

[GiGs]

Small update (pre-gen CDI installed !)

Now it feels like a Ninja, mid range is *just* to rich at 3.5 needle clip so i'm going to try 3 (i.e everythings exactly the same as before except my pilot and idle mixture ).

Also, now I realize the difference between surging and bogging (lean/rich) as it's easy to see on the wideband.

With the 112's if I remember correctly I was running about 12.3-12.5 A/F @ WOT, mid range was rich, idle is 12.5-12.8 sitting at about 13.2 at the lights, mixture is 2.8 turns out.

Plan is to try 3rd clip, possibly lean the idle by a hair (need more day time testing). powarrrr

cheers


Update:

Tried 3rd needle clip, still to rich right when mid-range comes online but difference is noticeable both on the wideband and physically (stays rich for less time). I am going to go down to the 2nd clip. The 112's @ WOT at around 140KM/h was at 11.9 stable. I tend to sit at high speed when I ride so this is ok.

Once I go down to the 2nd needle clip it will lean out everything a little so 112's should be fine.

I have 110's but there slightly damaged (first time mistake) around where the flathead goes in though I think it probably won't even matter.

Take off now is, wow, just perfect... haven't synced the carb's yet either but will do soon.

Will update again soon

[GiGs]

I've found it !!!! THE perfect set-up

110 Main Jets
2.5 Needle Clip
#40 Pilot Jet
2.8 Turns Out

I didn't quite catch exact figures (they were all in the 11-12's) because the bike pulls SO much everywhere I can't believe how much the bike changed since using a 112 main and changing to a 110 main.

Thank god I put a wideband on, it's a completely different bike !!!

I'm going to go on a longer ride (after I put the fairings on) so I can see if there are annnny problems at all but so far I cannot see a flaw.

I'll update later on, cheers guys, really appreciate the help

[indr]

Noob question. Is a jet the cylindrical thing with holes on it's walls? When you say #40 jet or #50 jet, what does the number represent? The size in mm? And if so, of what dimension?

[GiGs]

Is a jet the cylindrical thing with holes on it's walls?

Yes

When you say #40 jet or #50 jet, what does the number represent?

The size of the jet (it does not refer to the size of the hole in mm's), I am not actually sure of the size of the (pilot jet) hole in mm's (maybe this is something kkim can answer - bit busy to search it up at the moment). There is a comparison chart for the main jet size in the jetting database thread.


As for the bike (small update), perfect...idle just needs to be a little higher and that's it. Carbs sync'ed also perfectly.

cheers

[JMcDonald]

To clarify, the pilot jet does fit the description above, but the main jets are essentially just threaded cylinders.
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