If you have to do fixes to your Sachs FYM 400 then it is always a great idea to have a Workshop Manual for a reference in case that you need to know ways to take out a certain part like the Door and install it again correctly.
Sachs FYM 400 Workshop Manuals will give particular diagnostic wisdom with regards to your car therefore if something is playing up it can help you find out what the situation is and some ways to make it better. Then you are able to evaluate if you can do this on your own or that the job is simply too big you could book your FYM 400 into a suitable car garage.
Sachs FYM 400 manual