If you need to execute maintenance tasks for your Honda CRF150R2 then it is usually a good idea to possess a Workshop Manual to keep just for reference just in case you want to know ways to remove a certain component including Gearbox and fit it again correctly.
Honda CRF150R2 Workshop Manuals offer you specified diagnostic guides with regards to your car so if something is not working it can help you find out what the problem is and ways to make it better. You can then determine if this can be done on your own or that the job is just too big you can make a reservation for your CRF150R2 in with a nearby mechanic.
Honda CRF150R2 manual