KDXperts please help

[Wharf Rat]

OK well, I picked up my 1990 KDX 200 about two months ago. The guy I bought it from told me that he did some jetting work but that it was still rich from what he could tell. It was smoking a bunch, especially at WOT and at idle. He had run 40:1 kawie oil. It also was pretty peaky, very close to the MX bikes I used to ride.

So I take the carb apart and find a 145 main, 45 pilot, 1172 needle w/ clip second down from the top and the A/S is out about 1.75-2 turns. I am like "What the hell is going on here?". I thought it was rich still, before pulling the carb so these numbers can't be right from what I have read. At least that was what I was thinking.

It would idle fine when in the driveway, but didn't want to idle well on the trail. Low end throttle left a lot to be deisred as well. So I look at the extra jets he gave me. The only thing that was leaner than what was in there was a 42 pilot. So that was all I changed. There were dirty 148 and 150 and 152 mains I think and a dirty 48 and 50 pilot. So I try that new pilot jet (42). It freaking ROCKS. Solved ALL problems associated with the low end of the powerband. The bike worked so good off of idle that I hurt myself right away :aj: And still winds out clean and HARD.

But this seems to be leaner than most use. I am in 90*+ weather most of the time, and at like 800 feet elev. give or take a coupla hundred feet depending where I am going of course... :p :p :p

What do you think? It is jetted nicely now, but why did I have to go so lean (aside from temp and elev.)? It seems like every is always talking about things in the 150's. I have stock <A href="http://www.dirtrider.net/cgi-bin/clickpro/click.cgi?id=21" target="_blank"><b><u>pipe</u></b></a> and stock reeds.

I run a 12/48 combo on the final and about 40-42:1 on the oil mix.

I have never had a bike that ran so freaking well, but the numbers seem lean compared to what everyone else runs. I know that no two are the same, but... What kind of problems might this indicate?

Everything is clean and well functioning (carb, reeds, KIPS, float level, plug reads OK, maybe still a little rich if anything)

Think I might be losing spark power to not burn the mixture as well, thereby requiring leaner jetting than normal? I dunno. What do you think?

 

[Fuzzy Dice]

So which main and pilot did you go with.You mention several different sizes.

 

[canyncarvr]

He went with the 148-150-152/48-50 combo, of course! ;) (if you can't keep up, take notes!) Is your signature what's in it now?

CDave says:

1989 to 1994 KDX200

Stock -Run the stock R1172N jet needle in the second from the top clip position, 48 pilot jet, 155 main jet and fine-tune the pilot circuit using the air screw.

Sounds like your pretty close. Depending on which of the several you list that is actually IN your bike, you may need one-lean from stock because of reeds, another due to pipeage.

In any case, noone else can tell you over the DRN board exactly what to run. Different bikes are, well...different. IF your jets are selected in the time-worn correct fashion of TESTING THEM, you'll be fine.

There is a LOT to be said about 'seat-o-the-pants' testing. Still, some plug checking and a plug chop would be a good idea.

Sounds like there may be some serious fun in your future!!

 

[Wharf Rat]

As I said, the only thing I had on hand that was leaner was the 42 pilot, so that was all I changed since I knew it was rich down low.

Currently it is 145/42/1172N 2nd from top, as in the sig. Stock pipe and reeds, air box lid gone.

 

[canyncarvr]

The combination of air screw and pilot is a huge part of throttle response down low. If your's is good, and the bike starts fairly well I don't think I'd worry too much about it.

Spark power 'loss' is more likely to happen on top than on the bottom...(he thinks......)