87 kdx 200 low rpm issues

[walser12]

hello i just bought an 87 kdx 200 she runs great other than it seems to spit and sputter untill the powerband hits then has plenty of power everything seems clean. would it be the jetting? im pretty sure its stock other than a dg silencer slip on... had a paddle tire on it so perhaps tuned for wide open power? i ride washington trails and not dunes? any suggestions? heeelp!!!!!!!

 

[dirt bike dave]

Stock jetting on most KDX models is too rich, especially if you ride at higher elevations.

You can lean out the low rpm range by turning out the air screw. This is a small brass screw on the left side of the carb, near the rear of the carb, above the float bowl. Measure how far it is out by turning it in and counting the turns. If it was less than 2 turns out, set it at 2 turns. Turning it out will lean the low rpm range. After 3 turns out, it won't make any more difference and you would need to put in a smaller pilot jet.

On the needle, if you put the clip into a higher groove, that will also lean out the mid range. Changing the clip position is something you can do for free. It pushes the needle farther into the needle jet, letting less fuel past. FWIW, most KDX models benefit from a thicker needle, which leans out the mid rpm.

The '86 - '88 models are known to run pretty strong at high rpm. With some attention to your airscrew, pilot jet and needle, you should be able to improve your low and mid range power and throttle response, without hurting the top end power.

 

[walser12]

i dont mind losing top end its just barely ridable now... its full throttle or idle thats it?

 

[walser12]

just want it right
i live at sea level but ride the capitol forrest

 

[dirt bike dave]

i dont mind losing top end its just barely ridable now... its full throttle or idle thats it?

If it is that bad, you need to check and make sure the KIPS valve is working properly.

KIPS is the power valve system, which changes the exhaust ports. If it is stuck open, you will lose your low end power.

If the jetting has been too rich and the KIPS valve has not been cleaned, it can get gunked up. When it does not move freely, the teeth on the shaft that opens/closes the valves can strip.

On the right side of the cylinder, close to the pipe, there is a cover over the mechanism for the KIPS valve. Pull the cover off and start the bike. When you rev the bike to high rpm, you should see the mechanism move as the KIPS valve opens. If it is not moving, your KIPS valve is not working.

 

[walser12]

kips is good and played w it a lil today and seems like its ok just lil sputtery in low 1st n second 3rd gets more clear down low and if its stuck open the valve under the cover would not open when at high rev? as far as visual