KDXRIDER.NET

Just bought an '02 KDX220 that has a stumbling problem at high rpm's. It hits decent off the bottom but then cuts out pretty bad on top, almost like it's hitting a rev limiter. I've been riding, racing, and wrenching 2 strokes most of my life and figured it was just jetting (the top end was just rebuilt). Seemed like it was a little rich with the 48 pilot and 150 main so I installed a set of Boysen dual stage reeds, cleaned the carb and installed a 42 pilot, 145 main, and set the clip in the 3rd position (seems to be what a lot of guys run). Unfortunately that didn't help.......if anything, it might be a little worse. BTW, the bike has an FMF Gnarly pipe and Powercore 2 silencer, with No Toil air filter and air box lid removed. I ride in the east TN mountains, anywhere from 800 up to 3000 feet. Starting to wonder if the KIPS needs to be cleaned. Any thoughts???

I think you should clean it and see what happens

I've never cleaned a KIPS. Can it be done with the engine still in the bike or am I going to have to remove it?

can be done with it in the bike but need a head gasket

I would clean them and see where it gets you. Cleaning the KIP's is a general maintenance item and does need done every once in a while.

I could definitely see it being possible to clean everything out with the whole motor in the bike, and removing only the head. To me, it is easier in the long run to pull the cylinder off and do everything on a bench. But, if you go that route, you may as well order a whole new top end gasket kit. You can also check your piston/cylinder condition and ring gap while you're in there. Just a thought.

Check this out to make disassembly and reassembly wicked straightforward: http://www.thumpertalk.com/topic/657765 ... to-kdx200/

FYI - If you are looking at a factory service manual (like I was), some of the earliest revisions incorrectly identify which side certain valves go on. I can confirm that everything in the thread listed above is correct in regarding the left vs. right side identification. All of the torque specs match the factory service manual also.

220s fall flat toward the high end of the rpm range due to their porting, also they don't really like the air box lid removed as it can be difficult to jet & they don't really gain anything performance wise ( in my experience ) best to leave the lid on & just remove the snorkel.

Jetting should be 40-42 pilot ....145-148 main & needle in the 3rd or 4th position, air screw 1.5 to 2 turns out as a base setting .

To check it the kips valve is working remove the small round cover on the l/h side of the jug, next to the kips resonator cover.... Start & Rev the motor & you should see the valve rotate .... If it doesn't then it's either stuck or arm has broken.

I had the same problem but mine turned out to be neither jetting nor the kips. It took a few to track it down but it was the plug wire. Not saying for sure that's the problem but it behaved in the exact same manner as you described so it is something else to check.

Thanks for the input guys.

Unfortunately, the airbox was gone when I bought the bike, so I'm gonna attempt to work it out without replacing it. As bad as it falls flat, it's definitely more than a missing lid would cause. I know the 220 doesn't like to rev out, but there is definitely something awry.

I'll check the plug wire too. It stumbles bad enough on top that it could definitely be running short on spark.

Gonna try to find time to inspect the KIPS this weekend.

The plug wire appears to be good, so I tried to take out the valve inspection plug and that thing won't budge. Any tricks to getting it out? Should it be so tight that it causes a hurnea?

Try a little heat from a heat gun. All the spooge makes pretty good adhesive. If it's stumbling, then it's likely fuel delivery. Stumbling is different than reaching the top end of your power band. Important that you first make sure the intake and exhaust tracts are mechanically sound (no air leaks, reeds good, fresh gas and plug, no cracks/holes in boots, KIPS working properly, etc) before chasing jetting.

bufftester wrote:Try a little heat from a heat gun. All the spooge makes pretty good adhesive. If it's stumbling, then it's likely fuel delivery. Stumbling is different than reaching the top end of your power band. Important that you first make sure the intake and exhaust tracts are mechanically sound (no air leaks, reeds good, fresh gas and plug, no cracks/holes in boots, KIPS working properly, etc) before chasing jetting.

Well, it's a little more than a stumble. It WILL rev out, but takes 2 or 3 seconds and seems like it's cloggged up, so I'm now leaning toward the KIPS. It has fresh fuel, new air filter, new reeds, new plug, plug wire APPEARS to be good, pipe is clean, has good compression, carb is clean and has new jets, and everything seems to be sealed properly. About the only thing I haven't ruled out (besides the KIPS) is the silencer and I'm gonna repack it today.

I'll try a little heat on the KIPS plug and see if that will break it loose. I'm not a beast of a man, but it's VERY unusual for me to run across a bolt that I can't remove. My biggest concern was boogering up the slot. The biggest screwdriver I have has about a 1/2" wide blade and I thought that "should" be sufficeint. Is there a better tool than a screwdriver???

A coin and some big pliers

Finally had to use a dull chisel and hammer. Man, it was stuck BAD........but I prevailed.