Data Poll - RB Carb Mod for 200's

[canyncarvr]

If you would...a couple of questions for you.

What's your opinion of the RB part of the equation? Meaning, isolating that particular modification from the others gives you....what, in your opinion?

How much of that would you say is due to bore size, how much the other parts (plenum divider, jet screen etc)?

And, what does 'compete on kdx's' mean? Hare scramble stuff? I can't imagine you're referencing track use?

Just curious.

Glad you like it (or they like it...).

 

[ochster]

Tuff to critique the individual mods of the carb. Not being my personal bike, I do not have alot of hours logged between add ons. The first phase was a exhaust (oem muffler), and a set of boyesen reeds. It ran a little stronger down low and through the mid, with marginal gain on top. We had a spooge problem that seemed excessive, even when jetted decent. I tore the top end down, and upon inspection found the chamber to be milled offcenter of the head. Did a ring job, a new head, new silencer, and installed the RB mods (AEK needle). The bike definately had more top end. After reading the post about needles, I changed it out several times, ending up with the cej. No question, it added a nice boost, 3rd gear rollon wheelies are easy. The carb has shown to be very finicky concerning adjustment and jetting, I will be spending more time with it shortly. I have noticed the cylinder is pretty worn for a low hour bike, and the coating does not look very good at the port edges. It will be coming back apart soon for a replate, possible 200 cylinder to a 225. The bike is used for offroad, not MX. Keep up the good work...nice forum.

 

[Fred T]

I'm using a CEK #3 (was in #4) as the temps warm up above 70 consistently. I've seen lotsa guys running the CEJ #3 and was wondering what the difference is> According to JD's spread sheet it's richer for off idle to 3/16th throttle. I don't need any help there I think but does that little bit of fuel make it pull better down low or just make throttle response quicker? Reason I've been asking is because I've been working to get the bike snappier and this CEK #3 might have done the trick. BUT if a CEJ #3 is better then I'll try it. Anyone compare the two?

Thanks!
FT

 

[canyncarvr]

Fishhead listed CEJ-3 as his choice with the #7 slide, but he had a modified topend...didn't he? Not sure about that.

I have a CEJ, but never tried it for pretty much the reasons you say...the CEK tended toward being too rich on the bottom, regardless of what pilot/AS I tried. Didn't seem that the smaller diameter of the 'J' was the right direction to go.

Keep in mind my bike's a 200.

 

[fishhead]

I prefered the cej-3 because it gave the best throttle response for my riding style. I try to ride in the soggy part of the power band before it gets on the pipe and make the engine pull through rough sections and hills. I put a premium on controling wheel spin. My mods were a fredette porting job, RAD valve, RB carb mod and squish band, and rev pipe with a tcII on the 99 220. I ride tight woods single track in Western WA which is more eastern woods style roots and rocks with longer climbs and more water so conditions are generally slick, and at my age I don't like to pick myself up as often as I used to.

I think the CEJ-3 is worth a try and the benifit won't be seen until you have a tight slick uphill section with out a run or you need precise throttle control in wet clay or silt.

This is off topic but I think it might be worth a try to get a 00 kx250 n3we needle to try in clip 2 or 3 for the kdx. It will give more punch in the low-mid range and might be a better alternative than the plated carb in the 200 or 200's that are bored, yamaha '02 250 n3ew or '02 250 suzuki n8rh are close but the kaw needle is leaner and should work with a 7 slide.

 

[2 B]

Not very happy with the kdx. I'm about ready to shoot it and throw dirt over it(our myself). I have read all the posts on jetting and I can't seem to find anything good yet. I have just about every pilot,main,needle they make. And still no luck My main goal is to get 2nd gear to pull like first gear right off of idle. Could someone look at James Dean spreadsheet and help me out here (please).Temperature is above 70 degrees and humidity is 70% and above. I ride at 660 ft above see leve.l I have tried stock settings,C dave settings, Fredette settings,FMF carb settings no luck. Here is what I got listed below. And yes I have messed with the air screw every time I made a brass change with no luck

98 kdx 220
stock porting
607 reeds
rev pipe
turbine core 2 silencer
snorkel removed
13/49
Frp bored carb(stock slide)

and all the other mods done to it.

I have the following brass
pilot jets
38
40
42
45
main jets
145
148
150
152
155
158
160
Needles
stock
bel
cel
cej

There has to be something here I can use I have just not found it yet.

 

[Fred T]

OK, have you tried 42 pilot, CEL #3, 152? Maybe 155. Start there and tell us what happens. Air screw at 1 turn out. Move in out 1/8 turn in both directions to see what works best. We need a starting point and something to refeence from. Lets get the main right and go from there.

 

[fishhead]

can you refresh my memory on the 607 reeds, are those the carbon reeds or the fiberglass reeds.

cel-2,3or4
bel-2,3 or 4
ddl-3 or 4
dcl-2 thru5

cek ddk and dck might be worth a try.

 

[2 B]

Here is what I tried

CEL #3
158 main (looked good at WOT)
42 pilot

As soon as I put the cel bike would not idle very good. Bike idled very good with stock needled and the above settings. With cel needle I turn thr air screw out(less fuel right??). It helped out a little(you could hear rpm's pick a little. So drooped to a 40 pilot. But started to here a slight popping noise thru the exhaust just a little popping here and there. I have noticed the bike is a lille snappier with cel needle in comparison stock needle. So I'm back 42,158 a/s adjusted accordingly

 

[fishhead]

Have you tried cel-2 or cel-4?

 

[2 B]

Fiberglass and just changed those 2-4 rides ago
Corrections for above post
Rpm's would pick up a little
thr = the
lille = little

 

[2 B]

Fishhead
I would like to use what I got and only buy more brass as a last resort. $8 to $10 brass here and there adds up quick.

 

[fishhead]

is the problem a stall/bog or is it a sputter/hit that you are chasing

 

[2 B]

No, it is not a sputter

It is more like a waaaaaaa instead of a booooooog. I twist the throttle and you can hear the bike's rpm's slowly gradually increase(too rich on bottom end in my opinion). And then from 1/8 on up it cleans up and goes. It is from idle speed too 1/8 throttle I'm chasing after. Maybe I should just turn my idle up a little higher so my rpm's don't fall off so low?

 

[fishhead]

Should be able to clean it up by changing the pilot. I found the 42 pilot to lean on my 220 and i would suggest the 45 to start. If the problem is worse then try the 40. If it is too rich you will get a sputter, too lean and it will be lazy. Sounds a little lean on the pilot to me. I would try a #2 and #4clip on the needle first because it is easier and i'm lazy. :)

hope that helps

 

[motocross]

Are these carbs really that touchy to jetting, because I'm thinking about getting a 95' and up KDX but Idont want to have to fool with the jetting all the time,any help would be great.

 

[Jim Crenca]

Fishead,

Do you have some experience on pilot size in regards to run away idle when cold? Lately, the thing revs up very high when cold, and when re-adjusted for a warm engine idles great for the rest of the day. My starting drill is too slowly push kickstarter a few times (to get all those parts re-aquainted again), turn on choke (enricher), 1 or 2 firms kicks and it's running, immediately turn off choke. Leave it alone or change pilot?

 

[canyncarvr]

Jim: From old 'n slow...Use the kill button to control that runaway at idle. Mine got worse when I dropped a pilot size. Still does it some, but not as bad.....so the leaner pilot certainly makes it worse! I hadn't thought of the kill switch, and if I had wouldn't have used it. Seems it would cause some severe loading-up tbls. It doesn't though. Works just fine.

2B and respondents:

Looking for 2nd gear to pull just like 1st? This could be understood to be a bit much. Heck..how about 3rd? If you honestly mean you want to have the same response out of 2nd that you get out of 1st (same pull, same launch, same power), it isn't going to happen!

If you are talking about throttle response appropriate to the gear you're in, that's a different thing.

I don't know from reading your post what it is you're after. Noone else responding seems to have a question in that regard....guess they all understand???

re: pull in 2nd like 1st.

Yesterday, my 200, 80ºsome, 4000'el or so. 40/152/BEL-2/#7. If you expect ANY better response out of 2nd than my bike, you're just plain looney!! Goodness! Slower than a walk on a hill you could only SIT on, and 2nd gear was still good to go. Torque, pull, smoothness and power out the proverbial wazoo!! What fun!!!

So...a good pull out of 2nd is possible. If you want it to be just like 1st gear...well, good luck.

 

[OLD-N-SLOW]

I do not jet my bike to run good when cold. I dont care how it runs when the engine is cold. I will give up 1-3 mins. per day to have it run good when warm anytime. I do all carb adjusting
on a warm engine.
Ahh CC, life is good when your bike pulls clean even on an uphill when I stupidly leave it in to high a gear. That has saved my fat butt countless times.

2B,
If I were you I would try a cel-4 38-152 and go from there.Be sure you are reading the plug correctly. Do a search on plug reading and see.
Good Luck,
Steve

 

[fishhead]

Jim C
generally, a runaway idle on choke is one indication of a lean pilot, other indications are surging at idle after a hard pull or a high idle after a hard uphill pull that returns to normal after a short stint on easy ground, pinging or knocking on closing the throttle (overrun)

 

[Jim Crenca]

Fishead,

Idle quality is good at all times other than cold. I've gotten used to frantically lowering idle RPM until there is some heat in the motor (and then it needs to be raised). I'm so short on time I just wonder if it is worth loosing 1 hour of riding time for a re-jet.

 

[speedyts49]

I just bought a used '93 KDX 200 and wanted to see what jets where in there plus the needle setting. Question is; what is the technique for getting to the jets and needle. I had to loosen both ends of the carb and twist it to get to the needle. the main jet was not a problem. So do we take it out or twist it or what.
help please.
I will be riding at around 3000 ft. at 80+ temps(gorman,ca.)
main 150
pilot did not get that far yet
needle 1172n middle
1 1/4

 

[fishhead]

It's a bit off topic for this thread but your jetting should be pretty close. I am concerned about your main even with your temp and altitude because the earlier bikes seem to prefer a richer jetting package. We just finished a series of tests yesterday on a 92 and found the combo of 48 pilot and 1172n-3 with a 155 main was pretty good at 3500 feet and 70F. We do want to try a 158 main. a 152 gave a lot of pinging under load on this particular bike. No way I would run a 150 on that bike. :eek:

remove the tank and seat to make access to the slide or carb easier.

 

[Jim Crenca]

Fishead,
I started my bike for the first time in weeks yesterday (working too many hours and not spending enought time with the family), and with the same tank of gas from last post, the runaway idle when cold problem disappeared. Temperature was a little hotter than last time but my old bike is back! Oh yeah, the thing ran great during my ride around the neighborhood; go figure.

 

[Fred T]

Bike starts fine -choke on, no throottle starts right up and I let it stay on choke for 15-20 seconds and it will run ok. After I warm it up for 15 minutes or ride hard in the woods it won't idle.
RB Carb - #7 - 38/CEK#3/152 -A/S@ 1/2 turn 93 pump gas -40:1 Mobil 1 MX2T Stock ported 220 -FMF KG30 TCII combo. Temps in the 80's-90's

A couple things I am thinking is try a 40 pilot again - but it did it with that too or possibly go to 150 main, CEK#4, 40 pilot combo. I'm not good at plug chops - readings though.

I can say that I can hold it WFO and I never get any signals that I am lean at all, no pinging, no run on after I shut if down. It kinda seems like I'm getting more of the midband hit than before indicating maybe I'm too lean with 38/CEK#3 combo. So I'll try 40 pilot first and see what happens. It still seems to pull pretty good and I tend to run high gears with momentum in the tighter single tracks with no problems, never loads up and pulls gears fine.


Any suggestions???
Thanks