Figuring out Jetting - Does this sound right?

[mbl]

I have a new 03 KDX 220. When I got it from the dealer, they said it was already jetted for around 5000-6000 ft. I live in the Denver area.

I have just finished changing the fluids after breaking in the bike. So I have not done any WOT test, etc to check the plug. But in just looking at the plug after breakin and short runs around the block to warm up the engine, it seems to be a littel rich.

I have a couple of questions I would like to run by the group. From the dealer the bike has a 42 Pilot jet, a 135 Main, and the stock needle with the clip in the top position. The Air screw was turned out about 4.5-5 turns.

1. I think I should put a leaner pilot jet in, probably a 40. Since the air screw is turned out so much.

2. I think I should put in a leaner needle, since the clip is in the top position now.

3. Lastly, I am planning on taking the bike up to higher elevations, in the 9-11000 feet range. From working it out on a correction table, I am thinking that a good main starting point would be a 130.

I think that at that altitude the 40 pilot jet should be ok as well.

Does this all sound reasonable? I am just figuring out the whole jetting thing, since all my other bikes were road bikes with FI.

Thanks for any suggestions or comments.

Brian
Erie, CO USA

 

[Zerotact]

The AS is way too far out, you may end need to drop the pilot 2 steps. Stock a 220 should come with 42 pilot and a 145 main. It sounds lik the dealership stuck in a smaller main, wich can be gotten to by simply removing the carb drain plug, and unscrewing the jet. And then they backed the airsrew WAY too far out.

I'd also worry about the main jet before I worried about the needle.

 

[canyncarvr]

Go back to what you know is rich and do it right in the first place.

A bike 'prep' with a 4.5 turn to the AS is indicative of rather severe ignorance.

You shouldn't have a problem starting with a 1-down pilot and a 140 main. Put the needle on clip-2 (from the top/blunt end). Yeah, you'll likely end up more lean than this starting place, especially with summer temps...but start rich and work your way to more lean.

Set the main first, like zero said. A WOT plug chop with subsequent plug examination is the only way (reasonable way...not having some spendy equipment) to determine the proper main jet size.

Go here to see what a pretty much correct plug looks like.

Note: color has nothing to do with air/fuel mixture. You're looking for a thin ring around the base of the insulator.

Each jetting change and subsequent WOT plug chop test requires a new plug.

Start with a clean air filter and fresh fuel.

The other circuits are set mostly by throttle response. Plug checks aren't of much use at anything other than WOT.

Check the 'every kdx rider should read...' at the top of this board. Bookmark the referenced site (CDave's justkdx). Read up on carb tuning and needle decoding under tech tips.

While you're there, check out the 'new bike prep' article. The kdx needs to be properly maintained to run for long without, in some cases, some pretty spendy repairs. I'm sure the dealer told you he did that?

Yeah..the same maroon that set your AS 4.5 out. :(

If you have specific questions, please ask.

BTW, 'figuring' out what is required based on a chart is useless if you don't know what you are 'figuring' from. You won't get that info until you get it sorted out yourself.

I guarantee the way it is now is not correct.

Another btw...you're familiar with the 220 piston issues? Not to be an alarmist, but some riders with relatively stock bikes have had problems.

Most, certainly, have not. The failure percentage is pretty low based on rider complaints on this board.

But, if it happens to you, your bike has failed 100% of the time.

Enjoy your new bike!

 

[mbl]

Thanks for the suggestions. This was very helpful, as was the link to the discussion about reading a plug.

Brian

 

[canyncarvr]

Take a look at the seventh post down on this thread

There's a pic of the kind of thing you're looking for. Purportedly, you're looking for a pretty narrow ring...in the 1mm range...to indicate spot on jetting for the main jet. You won't be seeing the darkness of the ring in the post referenced earlier as a result of a short WOT plug chop check.

A WOT run as short as 10 seconds will be sufficient. The longer the run, the darker the ring.

If you don't remove the shell, it's pretty hard to see down inside the plug. There are specially made viewers (lamps and magnification devices) for that process.

 

[wibby]

BTW a Dremel moto tool with a cut off disk works well for taking the shell off the plug, just don't cut in to the ceramic, it will eat the disk up in no time flat.

 

[KAY DEE EXER]

I just use a 1mm grinding disc on a 100mm grinder to get mine off as I dont have a dremel. Even 2-3mm wheel would work just make sure you cut it right at the bottom threads......