1988 Rm 250 full rebuild about 4 years ago, 8-10 hrs run time, was running good, 1 ring piston, figured I would pull it down to inspect. Cylinder replated & piston matched by Powersealusa. I use Evans waterless coolant, it is clear With a blue tint when new, when I drained it it was darker & had a 2 stroke burned oil smell, like exhaust gases were being pushed into the coolant system...it did not overheat & I did not find coolant in the pipe....the underside looks brand new, no oil stains. The sidewalls of the piston are near perfect. all opinion are encouraged & welcome...thanks...