I finally got my 1991 Kdx200 going after almost a year of trials and tribulations and 3 pistons. We had the cylinder sleved after the first seizure and have made some bonehead mistakes since. But I thought I had it nailed this time. The bike ran great for about 8-10 hours of riding over 4 days in the woods of northern Minnesota. On the fourth day it developed a nasty engine vibration and a moderate loss of power. Also makes a ton of engine noise down low. I pulled the top end and found a groove 2-3 mm wide in the bore and a normal amount of scoring also. It does not seem to have any up and down play on the rod bearing. I am thinking there is a crank/rod bearing problem that is causing the vibration and cylinder scoring. Wiseco did the sleve and I am running a .60 over pistoon.