jetting help/questions for a 94 kdx200

rxraptor02 · Jul 6, 2005

Hello

I have some questions about the jetting for my 94 kdx200

mods to the bike that I know of:

stock silencer
fmf pipe
bosyen rad valve that will soon have new carbon fiber reeds

I called bosyen to see what they reccomended for jetting.

they told my that the stock setup was

150 main and the needle on the 3rd position from the top

they told me that they reccomended for the rad valve

145 main and to move the needle to the 4th spot.

here is what my issue is....

looking at the current settings I have a 158 main and the needle is on the top clip.

I have jetted my raptor with the dyno jet kit and my knowlegde is limited, but the way the kdx is jetted now seems way out of wack.

should I go back to the stock settings on the carb since boysen said to go leaner with the rad valve?

I am just looking for the better starting point to get the jetting dialed in.

thanks for any help
Jim

razrbakcrzy · Jul 6, 2005

You have a lot of questions to answer before you do anyting try this link click this and read Your plug will tell you all you need to know once you understand how to read it.

Green Hornet · Jul 6, 2005

If the clip is in the top position it is over compesating for one or both of the other circuts. I assume you bought this bike from someone else> So the question is why was the main changed from a 150 to a 158. The FMF should require no jetting changes & the Rad Valve would. What Oil are you using and what ratio? Are there any performance problems you don't like? What does the plug look like? Like Razor said, you have a lot of questions that have to be answered first :nod: :nod: :nod:

rxraptor02 · Jul 6, 2005

I know I had a loaded post.

yes I bought the bike used and ran it maybe 30miles off road then 70 or so on road.

I read the jetting page and it cleard a lot up.

I am still waiting for the new reeds to come in.

but with I was having issuse with the (midrange) 4th,5th,6th gear when 1/4 to wot it would hesatate/miss a bit.

My local shop owner said as I drove by him that it sounded like the choke was on. (the KDX is street legal)

so I first recleaned/oiled the filter with no change in performance.

so he suggested to check the reeds...

the reeds were bad not broken but lifted off of the rad valve a bit.

50:1 amsoil interceptor with 93/94 oct gas and the plug looked wet/oily... but I have not done the plug chop. that was after I got home and shut the bike off as normal. also after riding like 10 miles or so the bike does not want to idle. it wil start to idle low then stall out.

I agree with you on the needle position compensation for the fat main jet.

from the fmf web site they have some general specs with jetting changes and from what boysen told me on the
stock: MJ 150 needle 3rd
fmf: mainjet152-158 needle on the 3rd, airscrew 1.5 and remove snorkle
bosyen: MJ145 and the clip/needle on the 4th

with the info I have found I plan on this:

MJ: back to 150

needle/clip 4th spot down

I hope that leaving the pilot and air screw alone I will be OK. but that is gonna be my new starting point unless anyone has a better suggestion.

thanks
Jim

Green Hornet · Jul 7, 2005

If I were you, I would go back to stock jetting, after replacing the reed petals and go from there

Jim Crenca · Jul 11, 2005

1994 bikes have different carb passages confirmed by both Ron at R&B as well as Fishead,
158 main in not out of line for the year bike and the mods you have.
My bike has all the usual mods (including RB carb) and I'm running either a 156 or 158 main (can't remember which).
Check out the emergency RB carb jetting thread in the Archive section for more info all though it is really long.
A WOT plug chop is the correct way to jet IMO; a good thread on this topic is also in Archive section.
Cutting the plug to look way up at insulator is better than looking at bottom of insulator; a lathe works great but a Sawsall will sork as well.
Better rich than lean although spot on is best!

rxraptor02 · Jul 11, 2005

well I got the reeds and the carb jetted with a 150main and I have tired the needle on the 4th and 3rd and need to retry the needle back on the 4th spot. currently with the needle on the 3rd spot the plug looks tan so I am going to try the needle on the 4th spot. once its all back together I plan to run it and plug chop it at 3/4 throttle to see if the needle is adjusted correctly then I will to the WOT to see if my jet size is OK.

But the other bad news :bang: my clutch went out

It was fine last week and last night I had to adjust it was out.

Later
Jim

Rhodester · Jul 11, 2005

Seat of the pants works best for me on needle clip position. It' real obvious as you change the clip. I've never even considered doing any sort of a plug chop attempt to set the needle clip.

The "plug looks tan" tells you very little about your jetting. It tells you something about your plug heat range and the additives in the fuel you're running. "Tan" is pretty close on heat range. The plug chop (looking at the base of the new plug) will tell you the real main jet story.

Jim Crenca · Jul 11, 2005

I would suggest sorting out the main jet first and then deal with needle position.
I'm reasonably sure that a 150 main in a 94 KDX is way too lean; at least at 400' above sea level with pump gas and the above mentioned mods.

jetting help/questions for a 94 kdx200

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