If you wish to accomplish fixes for your Honda CRF 150 R then it is usually recommended to own a Workshop Manual for personal reference should you want to know how you can take out a specific component for instance the Gearbox and match it again adequately.
Honda CRF 150 R Workshop Manuals can offer you particular diagnostic information with regards to your car so if something is faulty it will help you figure out what the situation is and tips to correct it. You can then determine if you can do this by yourself or that the job is just too big you are able to book your CRF 150 R in with a decent friendly mechanic.
Honda CRF 150 R manual