I've got a 2004 KDX 200 and is battling to get the the bike running from bottom to top end. On low revs it would'nt perform! Standard jetting at sea level for this model I believe is main 160 and slow 48. What else can be wrong? On tops it performs well but gets worse from mid to bottom. The bike is stock standard, no pipes, filters or performance reeds. I've checked the reed but they're fine. The bike was stored away for some time. I've cleaned the carb and drained the tank for new mixture, 40:1. Please help!

Have you changed any jets?

try it with the air lid removed and see if that improves things. That will help determine if it's too rich overall. 160/48 is awful rich. Does it act like it stumbles/sputters?

Get some free time and jet that bike properly, and i would about bet that is the problem.

Hi mate if you look at my post you will see that I have the same problem.
Mine is a 2003 220 stock my pilot is 42 and it is stutters and feels weak at 0-1/4 gas. I messed around with the air screw and changed to a 38 which felt better to start with but once on the trail it felt the same.It pulls ok low down when the it is in higher gears or when pulling up hill but when you coast it feels unrideable.
I was told by one guy that a 38 was too lean so I have changed it back and I'm now looking at the oil mix I was on 32-1 which I have been told in too oil rich.
The best place to start looking is
New plug
air filter clean .
Run the bike warm and try the air screw trick to see if your pilot jet is too rich. Looking on the parts site there are two jets lower that yours it mightbe worth a try.
I will keep looking at you posting in the hope that you solve your problem.
Jono

Thanx guys. It's my off weekend so I will spend time this weekend and get back to you on Monday. One thing julien_d, howcome 160/48 is to rich if the bike is at sealevel? Surely that is the jetting the manufacturer suggests at sealevel. I'm new to this site and is actually quering this for a guys bike in town. I competed in competitions in Namibia 1993-1997 and of the last 4 years with a brand new KDX, so I had no problems. Bought a KDX brand new 6 months ago. This guy have been struggling with this 2004 KDX and I would like to help them. I thank you guys in advance for assisting me. I'll get back to you on Monday. What a great site with friends/supporters like you guys! By the way, I'm actually Afrikaans, so excuse the spelling!

Because the manufacturer jetting them disgustingly rich from the factory.

Julien do you think he should check for a stuck or broken kips?

seams that low end power loss points there, as that increases compression ratio in the -6000 rpm range.

kdxtops have you read the tech tips on the justkdx website?? read kips there and be carefull with that nut
its worth a shot to check the kips system

I also have a stock 2004 KDX at sea level. I have re-jetted to 155/42 and still may be a little rich. Temperature is just as important as altitude. The hotter it is, the leaner it needs to be jetted.

Thanx guys, problem solved. The first thing I asked the youngster was if his filter was clean which he responded to yes. I know that todays youngsters just wants to ride and do no maintenance on the bikes after riding. Well, it felt like I could give him a hiding in front of his dad. It looked like the filter was washed a year ago, submerged in filter oil and rolled in dust!!! I cleaned the filter and had a look at the jets. The 48 slow was almost clogged up with dirt. Changed it with a new 48 and problem solved! Can still be improved but its going like a boeing! Ill go down to a 158 main and I think it will our conditions at the coast of Namibia! Thanx a million guys! One child I could make happy and put a smile to his face. I warned his father though, no riding if the filter isnt cleaned properly.