99 cr250 jumping out of gear

Take a look at the shift star, the follower and the follower spring. If the spring is broken or weak it could cause your problem.

Keep us posted.

The most common causes of jumping out of gear are:

1. Like bscottr said, a weak shift detent spring.

2. A bent or worn shift fork.

3. Rounded engagement dogs on the the gears.

Or a combination of these.

The teeth may look fine but you should look very closely at the engagement dogs. On a 250, third gear is the one that is used the most and will show the most wear.