Part throttle good, but full throttle flat

[Teamgreenfan]

I have a 95 KDX 200 that runs great at part throttle, but falls on its face when I twist it all the way. It smokes (more than usual) and acts like it hits a rev limiter which is the only way I can describe it. Idle is good and isn't hard to start and the mix is 32:1. I bought this a couple of weeks ago so I don't know its history. Any help would be appreciated!

 

[julien_d]

Two things that come immediately to mind, needle jet/needle, and main jet. I'd pull the carb and inspect/replace those pieces. Also, it would probably be a good idea to check the KIPS operation. You can pull the little plastic cover on the RH of the cylinder, and watch the rod operation as you twist back on the throttle.

 

[Teamgreenfan]

I will try that. The thing runs too good to have something terribly wrong with it. I am ordering a Clymer manual for it before I get myself in too deep. I appreciate all the help.

 

[julien_d]

when it's running, do you feel the "hit" when the powerband kicks in? If not, I'd suspect powervalve operation. Also, repacking the silencer, and check the pipe for carbon buildup. If it runs nice and smooth off idle, it's probably something simple, as you say.

J.

 

[sr5bidder]

hey I don't feel a powerband hit is there something wrong?
mine is just alot of smooth steady power is this right or wrong?
could you explain where the power band typicaly comes in

 

[G. Gearloose]

What main jet do you have in it, and is the airbox or lid modified for more air?

 

[glad2ride]

There's no Clymer manual for a 1995 model.

I would check compression (worn top end - it is a 14 year old bike) and proper power valve condition.

 

[Teamgreenfan]

I just noticed I said 1995. I meant a 1987...sorry about that. My son has a 1995 KX 80. You know its funny, when the power band starts to really hit and starts to lift the front tire, then it immediately falls on its face as soon as the revs just start to take off. I let off the throttle and it still idles well and revs okay with the clutch in, but I think you may be on to something with the KIPS or power valve. I will start pulling things apart as soon as I get my manual and let you know what it was. I would like to have as many ideas as possible to make sure I cover my bases.

 

[sr5bidder]

I would stay away from the clymer manuals there are alot of details missing from them and they like to group 3 or4 different bikes into one manual.
There are plenty of factory manuals online for around 30 bucks

 

[Teamgreenfan]

It ended up being a KIPS rod covered in carbon and sticking. By the way pulling up on the shaft while riding and the throttle open is not a good idea! :coocoo: My son got a kick out of dad scream like a little girl when it hit the power band and my left hand on the throttle doing a really awkward wheelie :laugh: The bike and I survived the incident unscathed! I only wish we had a video camera....oh, well.

 

[julien_d]

hey I don't feel a powerband hit is there something wrong?
mine is just alot of smooth steady power is this right or wrong?
could you explain where the power band typicaly comes in

The KDX "hit" is mild compared to an MX bike, but it should definitely be noticeable. The powerband on KDX typically kicks in at 6k RPM. If you take off in 1st and immediately hit 2nd then wind 2nd out, you should feel a burst of power as the revs get high. It should hit in about the same place in every gear.

 

[sr5bidder]

well I'm still runnning a 160 main so maybee that mellows it out some and too I was ridding in the thick mud on saturday and was lugging it ..never really used 1st gear. I did notice though I used a whole lot more gas this time and didn't cover 1/10th of the distance I did last time I was ridding

 

[sharky243]

Check the reeds too. Bad reeds will make it bog out past 1\2 throtle and make it seem rich down low.