I have a 2007 klx300r. I bought it used about a month ago. I've only riddin it on the trails about 4 times. After the engine warms up it becomes hard to get it to shift from 1st to 2nd. It just slips into neutral and doesn't want to engage 2nd. If I get it into second it seems to do fine up to 3rd and the rest of the way. I'm wondering if I should try a heavier oil. I'm using 10-50 wt. Or I wonder if it might be a clutch problem. We ride a lot of low speed muddy and rooty trails so that causes the engine to heat up pretty good. Except for that I really like the bike so far. Thanks in advance for any help anybody can offer.