X2 to what these others said about idle speed and checking oil lever. There is no clutch lever to pull for putting in gear. The only clutch on these 400FA's is an automatic centrifugal clutch.
You may also want to check the shifter cable adjustment though, should be covered in the service manual.
These 400FA's are finicky and it sounds like yours was neglected at best. We'll help you through it though.