Jetting Confirmation

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May 26, 2005
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#1
Hey all..Great site. I just picked up a 1997 kdx200. I got a great buy on it. The bike looks like its only 2 years old instead of 8. I've been through all of the pages, and read, and reread everything about the jetting. I have made some mods, but now want to confirm what I believe to be the correct jetting. I live in Phx,AZ and ride between 1000, and 3000 feet. Right now its hot, so temps when I ride are in the 90s to low 100s with 25% humidity.

-I pulled the lid off the airbox, and will relocate the CDI box.
-I have a PC Pipe and Silencer.
-Boysen Rad Valve (previous owner installed)
-Uni filter
-previous owner premixes 50:1 is this right?

Carb jets currently installed:
Pilot = 48
Main = 155
Needle = R1174K clip 2nd from top

Tell me how to rejet this bad boy..... Any other help would be great...

Again, I have my own ideas on where to start with jetting, but let me know what you think. Lets see if you are on the same page that I am on...
 
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#2
You're in the ball park with the main but a 152 might be a little closer. You are definitely rich on the pilot. A 42 will probably be what you end up with (air screw between 1 to 1 1/2 out). This is assuming that you are using the stock #5 throttle valve (slide).
 
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#3
Before I get burned by everyone, even though I'm a newbie to the site, I HAVE read all of the Tech tips, as well as the carb tuning doc.

It turns out I was way off base on my initial jetting, and now I need some assistance, kind of...or else there is something more wrong with my new purchase that I didnt see before I bought it. Rode it today with the following jetting
Main, 155
Pilot, 48
Needle 1174 in mid clip
stock slide
Air screw at .5 - 4 turns out (see below)

Here are the problems. The bike always starts first or second kick, but wont Idle at all. The Idle adjustment screw has no effect. I can hold the throttle, cracked just a bit and It will idle. Air Screw has NO effect. I started .5 turns out, and went as far as 4 turns out, and never got the Idle to increase.

When riding it, there is absolutely NO throttle response until 1.2 throttle..Just booowwwaaaaahhhh, then Ringdingding...

I've been through the carb twice, making sure its clean. Im hoping its simply a jetting issue, and not something else. When it finally comes on at 1/2 throttle its got enough power to pull my 250# butt anywhere I wanted to go, so I would say that Mid and Top end are pretty good. Please pipe in and give suggestions.

Red_Rooster said:
Hey all..Great site. I just picked up a 1997 kdx200. I got a great buy on it. The bike looks like its only 2 years old instead of 8. I've been through all of the pages, and read, and reread everything about the jetting. I have made some mods, but now want to confirm what I believe to be the correct jetting. I live in Phx,AZ and ride between 1000, and 3000 feet. Right now its hot, so temps when I ride are in the 90s to low 100s with 25% humidity.

-I pulled the lid off the airbox, and will relocate the CDI box.
-I have a PC Pipe and Silencer.
-Boysen Rad Valve (previous owner installed)
-Uni filter
-previous owner premixes 50:1 is this right?

Carb jets currently installed:
Pilot = 48
Main = 155
Needle = R1174K clip 2nd from top

Tell me how to rejet this bad boy..... Any other help would be great...

Again, I have my own ideas on where to start with jetting, but let me know what you think. Lets see if you are on the same page that I am on...
 
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#4
Also, in the carb, what is the brass tube that is about an inch long that is in the body of the carb, and comes up right in front of the Pilot Jet? Is that removeable? It looks like the previous owner tried to take it out with pliers or something as it is all scored up.. It does have passage through it, though I dont know how much it is supposed to have...could that be related to todays issues??
 
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#5
If it is the Needle Jet you are talking about, yes it does come out. Could that be a problem if it is scored-Yes. Take the air screw out also and clean it good with carb cleaner, check you float level and see if the pilot was damaged. I run a 42 pilot, w/1173 Jet Needle in 2nd notch, w/a 150 Main. I am changing the clip position to center since I am right on the border of lean since switching to the 150 main. Check your carb over again. Maybe CC & Rhod can give you a better idea
 
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#6
My best guess is that your pilot circuit is blocked somehow. I'd go into greater detail in going through the carb and get into all possible nooks and crannies. The damaged brass tube puts suspicions on the previous owner and how he could have damaged the carb in other ways. Was there a kind of yellow tarnish build up in the carb? I'd also dump the gas and put in a fresh batch of premix. While the tank is empty I'd closely check for contaminants in the tank and petcock assembly. Next is vacuum leak checking time.
 
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#7
It has new premix, and ive cleaned the carb twice, though there wasnt any varnish in it. Ill put an inline fuel filter in it. What is the best way to check for vacuum leaks? Ive double checked all of the clamps on the the airbox boot, and both clamps in the intake boot. I havent checked the reed cage. Where else, and how do I check for vacuum leaks?

I will post pics of the suspicious brass tube tomorrow...
 
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#8
With the engine running, spray carb cleaner around the intake area (Reed Cage) of the engine. DO NOT do this on a very hot engine. If you hear a change in the rpm's then you have located the area of the leak. You can also buy a pressure kit where you can check to engine case and so fourth
 
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#9
So, in the first case, a vacuum leak around the cage can be fixed with a new gasket and/or tighten the bolts. I understand that a vacuum leak would effect low end performance.

In the second case, is the pressure kit used to do a leakdown test? Is that to test the crank seals? If they were bad, or leaking then woulnt I be burning Tranny oil?
 

Mac

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#10
If your air screw has no effect it could be that your pilot is way too big or too small and since you are running a 48 I would say it's too big. Try a 45 or more likely a 42 pilot and see if your a/f screw starts responding.