do not know enough about jetting

[dmaegan]

I have a 1990 kdx200 I bought used and ohmy was it rich.

elevation is about 200 ft above sea level
temperature is between 70 and 90 in summer
now between 35 and 50

when I got it it ran like a diesel found out the power valves were time incorrectly so I fixed them but my real prob is this

it has always sounded like a twin cylinder running on 1 cylinder and until I raised the needle one clip it sounded like flooded cat no ping and smoked like a train.

now once warm it mildly smokes but not to bad by the way it is white but my crankcase oil levels never drop.

But my question is I am pretty sure that is rich symptoms but when I installed fmf gold and fmf turbine it got even worse thats when I dropped the clip from the stock 4th to the 3 position.I want to make the jetting changes mentioned on the site but I had to lean it out greatly just for it to ping like a 2 stroke.And right now on the pilot circuit it still sputters and sounds like the above mentioned twin cylinder running on 1 cylinder.

the jetting recomendations say to make them richer then what I have does that leaner needle that is recommended going to lean those richer jets that much or do I have a oddball bike here.In the 1/4 to full throttle it pulls really good and hard but still smokes just slightly but the pilot circuit doesnt bog just sputters the jetting by the way on this bike is the stock r1172 needle and the 150 main and the 42 pilot

that is why I seem to be confused. oh I also have the air filter cover off.

any help greatly appreciated.I would not even post this if it did not seem to go against everything else I have seen and read.

 

[Joburble]

Woe, steady up! First things first.
Is the motor within manufacturers specs (good condition)?
What oil to gas mix ratio are you using?
Make sure you are not leaking trans oil into your motor through a bad seal.
White smoke? Does it use much or any coolant.

I know nothing about jetting, but I do know the guys who know will want this information before they can point you in the right direction. So post those answers and that will give the guys a starting point for you.

 

[helio lucas]

http://justkdx.dirtrider.net/carbtuning.html
here is a link on jetting.

 

[dmaegan]

motor is in specs as far as I can tell.
uses no antifreeze does not run hot.
starts first kick when warm within 4 when dead cold and not been ran for a week.
1/4 throttle up seems to be fine now.
1/4 throttle down very choppy.
would not idle until I raised the clip
now idles 750-800 rpm at a guess.
seems to be no power loss but when I got it,It ran like a lazy street bike.

 

[julien_d]

Compresion test would be good. That is not the stock jetting for your 90. Stock jets were along the lines of 158/48/ 1173n needle in the 3rd clip.

You made it richer when you raised the needle by dropping the clip to the 4th slot. I'm running 142/150 needle in 3rd clip on my 89 with airbox lid removed and aftermarket pipe/reeds. You try setting the needle in the 2nd clip from the top?

What's your airscrew setting? I wouldn't think you should need to go much leaner than 42/150, especially at that elevation. You might try a 40 pilot. Sounds like your carb might have other issues though. Pull the jets and clean them with a bit of wire? You can use the wire from a bread tie or a guitar string.

 

[reepicheep]

I know there is probably heresy to say here, and I'm not sure I will take my own advice here... but here it goes...

I have spent a lot of time getting jets, removing carbs, installing carbs, getting more jets, removing and installing, etc, etc, etc... Jets are cheap, but I think I am up to maybe 8 mains and 4 pilots... and would have more pilots but nobody local has the right sizes in stock. So even at $5 to $10 per jet, I'm pushing $50 to $100. Having done all that, I now have a KDX that... sort of mostly runs pretty good.

Don't get me wrong, the difference between where I started and where I ended was day and night... but I still have a little burble at WOT and high RPM. Since I had the pile of jets and was getting good at swapping and testing, I was simultaneously trying to tune another friends KDX-200... with similar work, I now have his running really well everywhere but "get a bog when you whack the throttle from very low idle".

So again, far better then where it started (which was bog anytime you whack the throttle from anywhere), but it's still not perfect.

I don't doubt I can eventually tune both out, hopefully without screwing up some other aspect of the jetting that is currently working so well.

So I chat with my local friendly dealer, and he says that they can generally tune them with about an hours work (which I am guessing is $65 or so). They said they try and keep the jets in stock, and just charge you for the ones you need, not all the ones they tried. And most importantly, they tune the bike with an exhaust gas analyzer and a ton of first hand experience.

Until you try it, you don't realize how easy it is to fool yourself. Did that last change wake up the top end and make the thing a monster? Or just ruin the bottom and and make a mediocre top end look good by comparison? Did you let the bike warm up enough to get it right? Is that bad jetting, or a fouled plug from the previous test (which was even worse jetting)? Are you rich, and need to go leaner, or lean and need to go richer? How many tests with how many jets to you need to really know?

So play with the jetting for fun and experience, but having done all that, I suspect I will still be taking my bike to a local expert (with an exhaust gas analyzer) who can really dial in a perfect baseline.

I suppose he may give it back to me with some minor flaw and he won't be any better off then I am... but I'm guessing that won't be the case...

It will be nice when the day comes that you can get an affordable home exhaust gas analyzer. They are starting to appear, but the ones that I have seen are based on car O2 sensors, and seem fragile, limited in what they can see, and still pretty expensive.

 

[julien_d]

Reep, not terrible advice there I'm sure. I do think though that anyone who rides a 2 stroke should spend lots of time practicing jetting, and learning what "feels" right when riding the bike.

Even if you get an "expert" to jet it perfectly, just a trip up or down in elevation and/or a change in temp and your perfect jetting is off again. Best to know exactly what that feels like and how to resolve the problem when you have it.

 

[reepicheep]

True! I found a chart somewhere and did some extrapolation, and it looks like winter versus summer can change your mains by something like 4 numbers... so like a 150 versus a 155, and that's without elevation changes.

It would just be a ton easier to know it is dialed in at 800 feet altitude and 80 Degrees F... You then know the middle, and know to creep to a smaller jet when it gets hotter or higher, and a bigger jet when it is colder and lower.

I am guessing you can just mess with the main, and leave the pilot jet and needle clip alone, for most changes between winter / summer / low / high. That would be handy, as I bet I can get that main out without even pulling the carb from the boot.

I'm a little jaded on the topic, because (counting my own) there are 3 KDX's and 1 KX-60 in my garage right now, and I have been trying to jet all three. And the KX-60 (Mikuni) keeps drooling gas on the floor, and the manual has the wrong diagram for the float height adjustment. Took me a bit to work out how that should really be done (21mm to the top of the semi circle curved top of the non compound curved float, for anyone googling this...).

Oh, hey, I accidentally drifted back on topic... Demagan, make sure your float levels are correct as well! That'll throw everything off as well.

Truth be told, I'll probably keep putzing around with it until I am happy, then take it in just to prove it to myself.

Can you imagine a modern KDX-200? Make it a 250cc fuel injected two stroke with a servo controlled ecm managed kips. With an updated suspension. Selling for $4k. Direct injection would be nice, but the servo valve controlled kips might do almost as well with a lot less grief. Ahhh.... to dream...

 

[Joburble]

I know there is probably heresy to say here, and I'm not sure I will take my own advice here... but here it goes...

:rotfl: That got a good laugh.

And a quick look back to basics before you start, dmaegan you didn't say what premix ratio you use.

 

[dmaegan]

the 1989 had a stock 158 main the 1990 switched to a 150
but your right I miss typed it is a 48 pilot I was thinking about my 125 sorry.
R1172n is also the stock needle according to the dealer which is in my bike.

I already blew out the carb passages and jets and reset the float height.

I am sorry I meant to say I raised the clip not the needle.it is in the middle position now from the stock 4th down.Air screw is at 1 turn out.

the top end is a monster from 1/4 throttle on all the way through 5th gear it digs a rut
continuous.It also has stock gearing.

I believe I am not getting full rpm though it seems to max at about 8000 by the sound of the motor.It does ping at idle like a 2 stroke but has a fuller sound above 1/4 throttle.

I guess to descirbe it best it is like riding a motorcross bike.1/4 up it screams.
but in order to pull out with any power it requires alot of clutch work to get the rpms right.Just pull out normally and put around it sputters.Which makes it hard to pull out and climb a hill realitvely quickly.

I would raise the clip to number 2 spot but I am not sure if it would lean out the top to much.Dont get me wrong I could probably live with it the way it is.But I would like to get the bottom right.

If it was mine I would leave it I like clutch work but its my sons and he is a novice Only rode motorcylce for 2 months Hes not that fancy with the clutch.

but if this is already this rich

would the websites jetting recomendations with the leaner needle bring it back into play on the ratio?

 

[dmaegan]

I am sorry I usually run 40:1 but I played this weekend with 32:1 to try to lean it out some more and it helped a tiny bit not much though

well I just ordered the n424-21 #45 pilot I will put it in on the weekend and post back.
I think that will fix the bottom end the pilot is deffinately rich at the 48 pilot.

I can not seem to find the type 13 152 main though or the needle jet r1173n anyone know where or is the 357 the same jet as the 13 I did find them.ebay is a no go for type 13 or the needle.

 

[Joburble]

Cool, a good place to keep your fuel mix is around 32:1 as recommended by the factory. (I assume you are using nice fresh gas too). The reason I say this is because a friend of mine (who is good at jetting) reminded me that when you change the premix ratio you also slightly change the mixed fuels viscocity and therefore its flow through the jets. You want to start with as many fixed (non variable) components as possible, so 32:1 is nice and safe and many kdx riders use that ratio with no real probs.

 

[julien_d]

the 1989 had a stock 158 main the 1990 switched to a 150

The 91 in my garage had a 158 main as well. I dunno.

Jetsrus or pats small engine are great for jets. Just go under kehien and the pwk. I ordered from jetsrus going by model and got the wrong pilots, so safer just to order the PWK jets. the 1173n needle is a kawasaki part, not a keihin part. You'd have to get that from an OEM parts supplier. If you're replacing the needle a keihin CGK needle would be better for your E series carb than the stock 1173. It's leaner through the midrange and fatter top and bottom though, usually needs about a 38-40 pilot and 150 main.

 

[dmaegan]

weird maybe it is just the 90 model parts cliche says 150 is stock and 150 is stamped on the jet.WOW it was rich with a 150 I could imagine it with a 158 I might as well pour the gas straight into the air filter. But I tried the kawy dealer they only had r1171n as an alternate to the stock one.I will go back and tell them a fib I just want the needle to put in my moped.
Maybe they were just stuck on me putting in a kdx and got confused.

but I am going to wait to the 45 pilot gets here and see what the transission from pilot to needle to main is like I sorta like the top end the way it is.Just do not like bottom.I saw a post with a 93 and got to watch a video now that I hear what the kdx sounds like I am good with what I need to do.I just thought at first that the kdx Might just be a little throaty sounding.This is my first one.

 

[julien_d]

150 is actually verging on lean for an E series KDX. Very few people get into the 14x range unless riding close to sea level in high temps. 150 seems to be working fine for me, but I'm at 4,000' with temps generally 32 - 70f.

I double checked a parts fiche and you are correct though, 150 is the stock MJ for a 1990. Odd. I wonder if there's some other change to the carb or even porting in the cylinder that we aren't aware of.....

I think you'll have more success with needle and pilot changes. The main doesn't see as much action as you'd think, although it can have some bearing on mid-range in combination with the needle choice and clip setting.

I haven't tried a CGK needle yet, but I have one on the way and other E series owners rave about that needle.

 

[domino dave]

My '92 "E" model ... I run a 42 and a 148 ... stock needle, one notch leaner. Boysen reeds. FMF. Golden Spectro 45:1. It rips! No bog ... not ever! For anyone who thinks it's too lean,or not enough oil, it's been set up this way for 3, going on 4 seasons now. No problems. Dmaegan- as said before, check your float level. Check the float itself to make sure it doesn't leak(shake and listen).Check float needle valve. Dave

 

[dmaegan]

yes Maybe there is some other diff in 90 not sure but like I said the 150 is rich
and i had to drop the needle on the 150 but the top end doesnt seem to bother me it is still mildly rich but workable for my riding areas I have no where to get into 5th gear let alone 6th but the 45 must go in for pilot my boy will burn the clutch out if I expect him to work the clutch like I do.But I know the floats are fine I set the height on them
I never get anything out of the overflow tube and I set the float in gas and submerged it to make sure it had no leaks when I took the carb apart to blow out the jets.

But thats why I was concerned about going to a richer main then I have already when I had to drop the needle to lean the jet I have out.

 

[julien_d]

I wonder what criteria are you using to determine the 150 is rich on the main? WOT plug chops?

The main jet does not come into play as often as you'd think. You're only completely dependent on the main from 3/4 - full throttle. If you make a mark on your throttle housing and a matching mark on your grip you can keep an eye on when you're on the main jet circuit. You can likewise make marks at 1/3 1/2 and 3/4 so you can keep an eye on what circuit or combination of circuits are being used when the bike is presenting rich or lean symptoms. Keep in mind that engine RPM is generally irrelevant here. top end / bottom end when we're talking jetting is not low rpm vs. high rpm. You can have the bike pegged and still be primarily using the pilot and jet needle circuits.

I hope none of that comes off rude or anything, just trying to help. I'm not sure we covered this stuff and I don't think anyone pointed you to the jetting stickey's yet?

 

[dmaegan]

I have a really good tuning ear but this bike had me baffled for a while because when I got it it sounded kinda like a fast moped but I got it worked out but rich would be never reving out or taking a long time and it sputtered all the way through the throttle range.

first thing I did to confirm rich was to remove the air cleaner box toatally and ran it for 10 to 15 seconds on the stand with 2 or three idle to wot's it was the single best mod I saw for the bike just a step above the fmf pipe.

I then put piece by piece the air cleaner back on.
in this order.

1 - the air cleaner box ( then ran it on stand for about 15 seconds with the wot's)
2 - then added air cleaner ( repeated on stand)
3 - then added lid ( repeated on stand And it went down hill there.)
4 - drilled a ton of half inch holes in lid ( on the stand Little better not much though)
5 - removed the lid ( on the stand Instant power)
6 - Plug chop ( Black Black Black and still very throaty sounding) so still rich
7 - next raised the clip on the needle ( 1/4 throttle up awesome still a little throaty)
it now pings at idle and will idle.

now the air screw never did a thing at any adjustment and still does very very little ao I have it a 1 turn out for gp reasons right now.

but I now can tell that my pilot is also rich because the much improved top end now shows me that the bottom end is like rideing it with a restrictor in the exhaust with a bad sputter then you alsmost get thrown off of it when you hit 1/4 throttle.

all this was done while the engine was properly warmed and by the way the choke never did a thing for it also which tells me the bike was pretty rich any how.

but like I said I never spend anytime that far down on the handle its fine for me but my boy needs the bottom end.

but as far as the rpm it is a very useful tool in jetting If you can use sounds to do your jetting.I have always been better with the sound and feel then the pulg chop.
there is to many unconstants in the plug chop.Thats in my opinion only.

 

[whenfoxforks-ruled]

It is a lot easier starting with the pilot and doing the main last. Each circuit feeds into the next, start from the beginning. Drop the pilot a couple sizes to get the air screw effective. If it does not respond by leaning out, the float valve and seat are bad. You will not always see it puking gas out the carb, it goes into the engine and pipe. It is not something you look at and pass judgment, unless its with a microscope? Its a yearly replaced item by the way also. Vintage Bob

 

[domino dave]

If it does not respond by leaning out, the float valve and seat are bad. You will not always see it puking gas out the carb, it goes into the engine and pipe. It is not something you look at and pass judgment, unless its with a microscope? Its a yearly replaced item by the way also. Vintage Bob

Yes ... What Vintage Bob said ... The floats in dirt bikes take a beating and are the culprits in many a rich running condition. Maybe not in your case, but make sure ... Hey Bob , just sold my '77 PE 250 after many years of good service ... Dave

 

[dmaegan]

thank you bob and domino you did answer my question a few post back about how lean you could go on the main with no probs on this bike.Ill report back when new pilot comes and I test it out.

 

[julien_d]

If you can use sounds to do your jetting.I have always been better with the sound and feel then the pulg chop

Me too. I only mentioned it because a lot of people get confused that if the bike is breaking up at high RPM it's rich on the main. This may not be the case. It could very well be the pilot and needle to cause this. It's not very often that you're gonna see WOT when riding.

Good plan on the pilot. I think you'll see some good difference there, and then you'll have an easier time nailing down the rest.

 

[whenfoxforks-ruled]

. Hey Bob , just sold my '77 PE 250 after many years of good service ... Dave

Best mud bog bike ever! Vintage Bob

 

[reepicheep]

Interesting, thanks. I have the jetting feeling like it is dialed in across the board, and it pulls really hard, but I break up at WOT high RPM. And I have an obviously badly worn 1995 carb (chrome is worn through to the aluminum on the carb slide).

Sigh. More money. :(