Carb jetting questions

[Old Man Time]

I have an 05 KDX220. I replaced the stock exhaust with the fmf desert and II silencer. I replaced the reeds with the Boysen power reeds. I finally replaced the stock carb with a 96 KDX200 carb. My problem is after reading many of the threads on here it seems that you are jetting your 200 carbs much richer than I can get away with. The first thing I noticed was I had to jet the 200 carb leaner than the stock 220 carb to get the bike to idle and run crisply.

KDX200 carb in a 220
idle jet = 38 (any thing bigger and you have to turn the idle screw in 90% just to get a sloppy idle.)

Float is adjusted
main = 142

Needle = R1173K #2 clip

Air screw out = 1 3/4 to 2 turns

Premix 40:1 synthetic

Altitude at which the bike is ridden 1317 feet to 6000 feet. Mostly 3000 to 4000 feet.

My friend who owned KDXs with very modded motors says I am running scary lean. Plug chop shows a creamy light brown or rust color. Seat of the pants says it is awsome.

Anyways my friend scared me so I rejetted to a 148 main with 2 turns out. Idle isn't quite as nice but still acceptable but now the bike loads up really easy if your not into the throttle.

Have any of you safely jetted it as lean as I have and been OK?

 

[canyncarvr]

re: 'Have any of you safely jetted it as lean as I have and been OK?'

'You...' who? 200 riders? No, not me..not even close. I have lean-roll stuck it with a 148 @ 3500', 70º.

220 riders with a 200 carb? Don't know about that.

re: 'Plug chop shows a creamy light brown or rust color.'

Color of anything is not the issue with reading the result of a 'chop' test.

 

[zeerx]

Have you LOOKED at the pilot jet? Thats a pretty small hole in there and easily blocked. If it is blocked, it will idle either fast or slow....if it's low and you try to raise it, it will race. If its high and you try to lower it, it will almost stall. You just can't find the sweet spot. Also it will not be crisp off the very bottom when you blip the throttle. Cheers.

 

[Old Man Time]

re: 'Have any of you safely jetted it as lean as I have and been OK?'

'You...' who? 200 riders? No, not me..not even close. I have lean-roll stuck it with a 148 @ 3500', 70º.

220 riders with a 200 carb? Don't know about that.

re: 'Plug chop shows a creamy light brown or rust color.'

Color of anything is not the issue with reading the result of a 'chop' test.

Yes I am talking about a 220 with a 200 carb. They are supposed to be jetted the same but I can't get close to a 200s jetting.

I may not of used the correct term when I said plug chop. I am not talking about literaly cutting the plug to expose the entire ceramic. I talking about about really riding the pipe in 1st 2nd and 3rd, hitting the kill switch and checking the plug color.

Anyways I know this jetting is not the recommended jetting for a kdx200 or a kdx220 with a 200 carb on it. I was just curious if you could safely run a 200 or 220 with this kind of jetting. For some reason the bike runs (seat of the pants) right when jetted this way. The second I start getting richer on the idle jet or the main and the bike starts idling poorly and loading up on slow technical riding.

 

[ridejunky]

Anyways I know this jetting is not the recommended jetting for a kdx200 or a kdx220 with a 200 carb on it. I was just curious if you could safely run a 200 or 220 with this kind of jetting. For some reason the bike runs (seat of the pants) right when jetted this way. The second I start getting richer on the idle jet or the main and the bike starts idling poorly and loading up on slow technical riding.[/QUOTE]

Do a search on plug chops/readings and C.C.'s prints will be all over them. His knowledge is exhaustive, canyonous and always spot on. I must ask why you would you want a 200 carb on a 220 for slow tech stuff and hill climbing. It seams counter productive for that type of riding.

 

[Old Man Time]

Anyways I know this jetting is not the recommended jetting for a kdx200 or a kdx220 with a 200 carb on it. I was just curious if you could safely run a 200 or 220 with this kind of jetting. For some reason the bike runs (seat of the pants) right when jetted this way. The second I start getting richer on the idle jet or the main and the bike starts idling poorly and loading up on slow technical riding.

Do a search on plug chops/readings and C.C.'s prints will be all over them. His knowledge is exhaustive, canyonous and always spot on. I must ask why you would you want a 200 carb on a 220 for slow tech stuff and hill climbing. It seams counter productive for that type of riding.[/QUOTE]

Actually the 200 carb seems to add strength everywhere in the power band.

In a 50 mile ride we may run into 6 or 10 miles of the very slow technical stuff. The rest is a bit faster winding and twisting trails and hills.

I have noticed that the KDX runs better when a bit leaner. Most folks are looking for the biggest main jet they can get away with but I do not like a bike that is jetted that way. My stock carb is jetted the way the kdx200 carb is except that I run a CEL needle and a bit richer #40 pilot. It runs great this way. Crisp and does not load up easily.

The 200 carb makes it pull harder and quicker which I like. But I do not want to burn my bike up over this. If the KDX's are designed to be run super rich like the factory settings then fine I will do that cause it is a fun bike in the woods.

I just need some advise from a KDX carb pro who know what I am after. Going to a 200 carb on the 220 is quite common with 220 riders.

 

[glad2ride]

"Yes I am talking about a 220 with a 200 carb. They are supposed to be jetted the same but I can't get close to a 200s jetting. "

A KDX200 with a 35mm carb is not going to be jetted the same as a KDX220 with a 35mm carburetor. The fuel is going into a larger cylinder with different porting.

"Plug chop shows a creamy light brown or rust color."

When you say plug chop, do you mean the color of the ring or the color of the majority of the ceramic?? I see no mention of the ring height.

 

[ridejunky]

"A KDX200 with a 35mm carb is not going to be jetted the same as a KDX220 with a 35mm carburetor. The fuel is going into a larger cylinder with different porting."

This couldn't be more true. It also has a lower compression piston. The Idea behind the 220 was to make the bike handle like the 200 with more low end grunt and less mid range hit, thus the bigger bore, different porting and smaller carb. Many folks try to re engineer the 220 to be like a 250 and in the process loose the tractor like torque. Sure it has more mid and top but at the cost of the one quality it was designed for. Mine runs great everywhere with the 33mm especially down low and I don't have to abuse the clutch.

 

[Old Man Time]

"A KDX200 with a 35mm carb is not going to be jetted the same as a KDX220 with a 35mm carburetor. The fuel is going into a larger cylinder with different porting."

This couldn't be more true. It also has a lower compression piston. The Idea behind the 220 was to make the bike handle like the 200 with more low end grunt and less mid range hit, thus the bigger bore, different porting and smaller carb. Many folks try to re engineer the 220 to be like a 250 and in the process loose the tractor like torque. Sure it has more mid and top but at the cost of the one quality it was designed for. Mine runs great everywhere with the 33mm especially down low and I don't have to abuse the clutch.

My wording has been misunderstood by several which is my fault. I didn't mean that the KDX200 carb would be jetted the same as my 220 carb (although that is what has happened). What I meant was when this mod is made the KDX220 is supposed to be jetted the same as the KDX200 since it now has a 200 carb on it.

Plug Test:
Almost the entire ceramic except maybe the last 1/8 inch was creamy brown rust color. The last 1/8 inch appeared to be white no color at all. It was somwhat hard to see.

I can turn the entire ceramic wet black by just jetting it where it is supposed to be jetted.

Clutch abuse in my case happened before I ever went to the 200 carb. My clutch started slipping with the stock carb on it. It has been a weak clutch from the git go it could not handle much slipping in slow steep tech stuff. That is what I mean by weak. If you do not slip it so it does not get hot it works just great. But if you have to stop the bike on a extremely steep grade and you need to slip the clutch to get going it heats up very quickly. Just a couple slips and then the clutch starts slippin on its own.

I bought this bike new off the show room floor. It is a great bike and I have not lost any low end by going to the 200 carb. If anything its stronger. I am just having jetting issues because I have to go so lean to get it to run right. Maybe there is a defect in the carb. Must be since no one here seems to get what I am talking about. I was just hoping someone with more experience with this mod than myself might be able to help me out.

R B Designs is the next stop since he converts the stock carb into this mod. He charges $165. to do it but every one raves about what it does to the bike. It does not turn the bike into a 250. If I wanted a 250 that is what I would have bought. It generaly keeps all the good qualities of the bike only improves on them. I don't think the KDX220 or 200 will ever be an mx bike nor would I want it to be.

I hope this clears up the waters I muddied a bit.

 

[steve.emma]

even though the 200 and 220 motors differ in many ways, according to the justkdx website you do (as a starting point) jet a 220 with the 200 carb the same as you would for a 200.
as far as your concerns about the lean jetting are concerned i will admit it does sound lean but the seat of the pants is your best indicator. if it was too lean then you would likely get detonation and/or the power would flatten out.

 

[G. Gearloose]

A stock, corked-up airbox would fool one to use jets that 3-4 sizes smaller..i coulldn't find mention of your case so i had to inquire.

 

[krazyinski]

even though the 200 and 220 motors differ in many ways, according to the justkdx website you do (as a starting point) jet a 220 with the 200 carb the same as you would for a 200.
as far as your concerns about the lean jetting are concerned i will admit it does sound lean but the seat of the pants is your best indicator. if it was too lean then you would likely get detonation and/or the power would flatten out.

My kdx ran fine I thought like it was suppose, to the motor and carb being built and put together from a reputable company 160 main 45 pilot 1173 third from the top this is with a 36mm. after a few weeks of test and ask I now have 155, 42, DEM 2nd from the top this is good BUT I will still play with some different needles .coming from four stroke back ground I know about jetting but that oil in the gas get it to lean and screw the top end is intimidating, but I agree with steve.emma your best bet is what your doing ask, read, research, test, the best being your seat of the pants and then your still on your own.

 

[John Harris]

You have some jokers in the mix and every bike should be jetted individually, but I think you are close. I would try a 145 on the main. You should have nothing but good results from the 38 pilot at your altitude until the weather gets cold. That may force you to go to a 40 pilot. You are correct in that on a 220 or 200 cc engine the jetting is worth working on. Cheers John

 

[Old Man Time]

A stock, corked-up airbox would fool one to use jets that 3-4 sizes smaller..i coulldn't find mention of your case so i had to inquire.

The airbox lid was the first thing to come off when I got the bike home.

 

[Rhodester]

The first thing that strikes me is the possibility that your supposed "'96 200" carb is not from a 200 at all. Are you absolutely sure beyond a shadow of a doubt that you did not mix up the carbs and really put a/the 220 (33mm) carb back on the bike?? What you are describing sounds impossible to me. The only other possible answer I can think of is that your filter is grossly over oiled or the exhaust is partially plugged or something else along those lines. Have you checked the float setting/height and checked the condition of the needle and seat assembly (possibly dumping extra fuel into the mixture)?? The 220 and the 200H should be fairly closely jetted figuring a PWK35 is on both bikes.

 

[Old Man Time]

The first thing that strikes me is the possibility that your supposed "'96 200" carb is not from a 200 at all. Are you absolutely sure beyond a shadow of a doubt that you did not mix up the carbs and really put a/the 220 (33mm) carb back on the bike?? What you are describing sounds impossible to me. The only other possible answer I can think of is that your filter is grossly over oiled or the exhaust is partially plugged or something else along those lines. Have you checked the float setting/height and checked the condition of the needle and seat assembly (possibly dumping extra fuel into the mixture)?? The 220 and the 200H should be fairly closely jetted figuring a PWK35 is on both bikes.

Yes I am absolutely sure. I measured it even though visually you can see the difference in the opening. The carb measures a bit over 35mm but not quite 36mm.

I have set the float to shut off a bit earlier but I did notice on the ride that the bike dripped fuel when on the kick stand. Nothing dramatic but it did drip sometimes. It does not drip with the stock carb on. I had already planned on taking a second look at the float valve. It looked to be in very good condition but I may of missed something. It did not drip unless sitting at an angle on the kick stand. A new valve is cheap so no problem replacing it.

The exhaust is brand new. The stock carb works perfect and the only thing different is the carbs.