2004 yz250f this has occured 2 rides in a row now and i changed the oil in between. the shift from 1st to 2nd gets really hard while the engine is on. I kill it and it is really easy to get between gears. So strange. then i will ride for a while and 1st and 2nd will be like butter. I can find neutral without a problem. then bam, hard as all hell again. to the point where it actually hurts the top of my foot through my boots. Any ideas? i change the oil all the time. and the filter about every 20 hours.