KDXRIDER.NET

Hi,

Need some help because experimenting has left me confused.

2002 KDX 220
RB Carb
RB Head
Cut open airbox top
Elevation: 100-180m or so 300-500ft
Boyesen Reeds
Pro Circuit Plat 2 Pipe
Stock silencer

Current settings: (as they came from RB Designs)
Main Jet 150
Pilot 40
Float Height 17
A/F: 7/8 turns out

My bike always ran great. It started real easy, warmed up easy, and then rode great.

I then wanted to play with the a/f mixture a bit to see if I was missing on something without even knowing it. First step was to measure where I'm at, messed that up, screwdriver slid off on me. Fine I will just set it again. Start at 1.5 and go out towards 2.5. Settled on 2 turns out. Blips were nice. However during riding it felt off, weak. So I played around and set it to 3, 2.75, 2.5, 2.25 all the way down to 1.5 always the same.

I went to look for Ron's instructions and where he filled out the a/f setting it seems to say 7/8 turns out. I never thought of going below 1.5. So I set it and my bike is running excellent again.

Now I am confused, I thought if the a/f is less than one turn you have to change pilot. Please advise?

Picture of settings notes from Ron. A/F hard to make out.
https://imgur.com/a/6DVukEU

I have the same RB mods on my 220 and was confused about the 7/8th turn setting and Ron's instructions that you're not tuning for fastest idle. You still should follow the jetting guide looking for fastest idle to determine the correct Pilot Jet size.

https://tinyurl.com/Jetting-Guide

In my case, the jetting guide determined that I should drop down to a 38 pilot which really improved response. You may wish to get an adjustable air screw from JD Jetting to make tuning easier.

The finger adjustable air screw is really nice. I agree with following the jetting guide but in your case with Ron’s suggested 7/8 turns out I would start by going 1/8 turns from his baseline to test. Go 5/8, then 1/2. Go to 1, then 1 1/8. If it gets better at 1 or 1 1/8 I’d keep the 40. If it gets better at 5/8 or 1/2 I’d put in the 38 he gave you. As we get into fall and winter with cooler temps you likely will have to richen up soon from the 7/8 position.
On the other hand since it’s running excellent at 7/8, just like he suggests, I’d be tempted to leave well enough alone. That guy is good lol

Thanks for the advice I will play around with it more.

Is this the screw for us? https://jdjetting.com/product/jdam55-jd ... eihin-pwk/

Yes that’s the one. Tusk makes one also from RMATV. I forget the name brand of mine but it looks like the Tusk one. Maybe Zip-Ty Racing.

Tusk makes an idle screw that's on RMATV. I'm not sure about an air screw. The idle screw does not fit even though it's on their list of parts that fit the KDX. I informed them of that, but it's still on the list.

They do sell the air screw for KDX but it’s a kit with the idle screw also. I bought the idle screw a while back before I realized it doesn’t fit the 33/35. It works great on a 38. What I found that does work great for our carbs is the metal (silver colored brass) idle screw. It’s listed on jets r us in the PWK carb parts list but says for non chrome slides. I’ve had it for a couple years now and it not making an indentation on the bottom of the slide. It’s knurled and easy to adjust with your finger and thumb, wearing gloves or not. Easier to spin if you blip the throttle a little and get the pressure off of it.

My RB info sheet said 7/8ths too but it was set at 1.5. I thought that was weird but it seems like it’s common.