Really Confused on Carb Jetting

you need to read the plug
if it is black and fouled then it is to rich go in the next lower number main jet
if it is white you are way to lean and need to go up to the next number main jet
what you want is tan or light brown this is where you start
then adjust up or down to make the bike pull the way you want
there is no magic setting on a modified racing motor or slight mod motor
the factory setting are average to all conditions thats all

Mark,

Jetting can be very confusing. Understanding what is going on in the carb helps greatly to better understand what to do. Please go to this article http://justkdx.dirtrider.net/carbtuning.html
I expect this will help you. Also check out "Canadian Daves" and "Pit Bull Racing". You have already been to Canadian Dave's I see.

After you get through the article on carb tuning and feel you have a basic understanding of what is going on put in the jet scenario recommended from either Canadian Dave or Pit Bull. From there start fine tuning. You may need to go up or down in sizes or needle position, as a remote possibility maybe a new slide with more of an opening. But armed with the knowledge of what is going on and a recommended starting point for jet sizes you will be able to dial it in.

Usually when I am chasing my tail with jetting there is something else wrong. Air Filter, Compresion, Plugged Exhaust, or something like that.

Mark it has been my experience that most manufacturers ship their bikes with conservative jetting. Meaning a little on the rich side. Running rich keeps the engine cooler and lessens the chance of seizure. Almost every bike I have owned has been this way. They all required rejetting once I got them. I usually take the jetting to the lean side until the radiators are a little too hot for my knees and the bike is very crisp and responsive. Kinda like it is almost out of fuel. This is too lean. This condition will show up in about 10 minutes of riding and if not corrected will damage your engine. I then increase one jet size on the main and pilot until the bike isn't quite so hot. Going up I don't recall ever increasing more than two jet sizes to cool the engine down.

Why is your bike so rich out of the box? I think it is because the factories want to ship it with no concerns of being too lean and causing failures.

Why is a smaller bore engine jetted larger than yours? I can't say for certain but I bet it has something to do with them not wanting to be too lean.

Why is your bike continuing to foul plugs? I would suspect that your carb jets are rich and there is a possibility that your carb slide is too lean. It sure sounds as though your pilot jet is rich. Also, what is your mix ratio? If it is less than 32:1 that might have something to do with it. If you are at 32:1 or higher then I wouldn't suspect the mix ratio.

MarkWo said:

the settings for the KDX200 carb are way richer than the 220. Tell me how this makes sense. Smaller motor equals more gas to Kawasaki - I definetly do not get this one.

Click to expand...

The 220 carb is 2mm smaller, thus creates more vacuum, so smaller jets are needed to make the same ratio as a 200's larger carb, thats all.

The 220 comes stock with a 33mm PWK and the 200 comes stock with a 36mm PWK hence the difference in jetting between the two.

"Does one clip position make that much of a difference?" Yup

Fine tuning the air screw is going to be important as very small adjustments will make a big difference on the 220. Try nothing larger than 1/8 turn adjustments when fine tuning.

Ideally to get the best performance from your 220 with the 33mm carb you'll want to try a different jet needle. Have a look at one of the many RB carb designs threads for jet needle recommendations.

David

Canadian Dave said:

The 220 comes stock with a 33mm PWK and the 200 comes stock with a 36mm PWK hence the difference in jetting between the two.

Click to expand...

The 200 comes with a 35mm PWK...at least mine (2000) did.

RB's modded 200 carbs are 36mm.

Port timing between the two bikes is different. So is the static compression ratio.

Anything that effects the breathing capability/characteristics of the engine will likely effect jetting.

re: '...the plug fouls quickly..'

If you have no (other) mechanical problems then, 'how far off can my factory stock carb settings be that makes it run so rich out of the box?'?

Obviously rich enough to cause the problem. ;)

There is no reason to foul a plug. By 'reason' I mean that if the bike is in good mechanical condition, your jetting is 1/2-way right and the fuel and fuel mix is correct you won't foul a plug. I've run the same plug for well over a year. It never fouled. I was on more than a couple of putt-putt type rides during that time. The plug never 'acted up' let alone foul. Not a 4-stroke hiccup ever.

Different subject (kinda) but I just got back from a 3-day coast dune trip on a Banshee (it has two spark plugs). Most of the time was pretty slow cruising around. Plugs were fine.

But then, they've been fine for the past few years in that machine, too.

Point (in case you missed it) is that OEM jetting must be pretty much off, 'eh? :think:

So: 'Any comments on if I'm running rich with the stock set-up?'

Yes.


My 200 came with a 35mm small body PWK. Ron (RB-Designs) bored it to 36mm.

re: 'you need to read the plug if it is black and fouled then it is to rich go in the next lower number main jet'

If this makes sense to you as a reasonable approach to jetting, please do some more research before you start changing things around. At the very least ask some questions.

---

I suspect after the divider is pressed in, it resembles 35mm.

Yep.

That's the purpose of the bore; to not reduce the volume of the carb when the divider is installed.

...at least, that's my understanding. Otherwise I suppose it could be bored larger.

Actually, I do recall reading something along the line of 36mm being the largest bore you can get out of a small body PWK. Maybe not.

In any case I suspect Gearloose suspects correctly.

Whew! That was a hard read, 'eh? ;)