lt 125 popping out of gear

[fobrnno]

i have a 86 lt125 for the kids that i got cheap then after a few rides the main tranny drive shaft broke. took it apart and replace the shaft with a new one from the dealer. checked the shift forks looked good and the gears also looked good. put it all back together and went for a ride yesterday. ran fine for most of the day but when goinging up a hill or lugging cause in the wrong gear it would pop out of gear and into neutral. is there any adjustment that can be done or do i need to tear it apart again and replace some parts? and what parts would i need to replace?

thanks james