hi im new to this forum stuff but maybe i figure it out quickly

i have a 1988 yfm350 moto4 that will only goes into what i think is fifth gear. when i pull shifter on fender down to reverse it goes into low gear and all the up its in high gear. i tried to adjust clutch screw no result i tried shifting while on the go no result once it isin gear i have to cut itoff and keep pulling foot shifter up and down till it finally comes out of gear any tips to try before i take side cover off to look inside or is that my best option.