My neighbor recently picked up a 96 KDX 200 for a great price. It was in nice condition, but was a little low on power in my opinion, but I told him it probably needed a top end since the folks that owned it probably neglected it a bit. All it needed was a new air filter, some leaner jets, and the bolt to hold the filter in, so he replaced all. We also put a KX250 silencer on it, which added a little of that "factory 250 sound". He rode it a while, and we frequently compared his to my 97, which is ridden very little, and the power difference was night and day.
We both had some spare time this week, so I convincd him it was time for a top end job to fix this loss of power. I had to work late a couple of nights this week, so he and a buddy were going to perform the teardown, provided I was there to do the critical measurements, and put the motor back together.
So today while I was at work, he calls me and says they took off the pipe, and it was about 60% restricted around the lip of the exhaust pipe, and it was heavily plugged with carbon (about 1/4" thick). I told them to clean up the carboning, and flush out the pipe. They did, and then proceeded to remove the jug. With the Kips disconnected, the jug was removed. After rotating it 180 to view down into the cylinder, they noticed a rattling noise. They shook it a bit to duplicate the rattle, and the air filter bolt and washer/wing nut fell out of the reed cage onto the floor!! Apparently this bolt was laying in the reed cage, in the gas path, blocking airflow thru the motor, which in turn caused the heavy carbon buildup. Needless to say, the piston was covered on top, and the Kips was pretty chalky too. The rings measured .024 and .030(old), and new .012 each, so we are going to surface the cylinder walls, clean the kips, and slap her back together.
I will update in another post regarding the power gained from these teardown finding corrections. :thumb: