I bought a low mileage 2003 yz250f and it has always been hard to get into first gear when down shifting from second gear. When first gear is needed due to the technical trail or a hill with rocks and wet angled roots I sometimes would let the clutch out partially then pull the clutch back in and it will downshift. My friends have had yzf and wrs with no problem at all. If the oil is not changed every 2 or 3 rides it does get harder to shift also. One of my motorcross friends always tells me to not use the clutch when upshifting or downshifting, just back off the throttle and shift. My bike downshifts from 2nd to 1st without the clutch smoothly. If I use the clutch it is almost always an issue. I believe the prior owner probably bent the shift fork. I do not plan on spitting the cases to fix this. If you are racing this might be necessary to fix or if you are just trail riding "if it ain't completely broke don't fix it."