OK for the most part these engines are bulletproof. There have been owners who have gotten over 200,000 miles on them. All tyhe brake parts are the same for '83 - '85, and the master cylinders can be replaced with '86 to '93 as well. The clutch slave cylinder is the same for all years, and is easy to replace except it can be tricky to get out as it has to be wiggled, turned, and twisted in a praticular order to get it to fall out. Rebuilding your carbs is going to be the most expensive and time consuming part. To do it properly plan on spending $300 or so when all is said and done. There is an excellent step by step video out there to do it properly. The biggest problem with them is pin holes in the diaphragms, asnd plugged jets in the idle circuit. There is a set procedure for syncing the carbs and you have to monitor all 4 vacuums at the same time. There are several members proficient at this procedure that will be gladto help you out.
If you can just plain get it running, you may want to use a product called seafoam on the carbs. You can buy seafoam at wally world or auto zone. You may want to flush and red cote your gas tank too. New plugs and wires are a good bet too, but do not instasll new plugs until you drown your carbs with seafoam and let them soak for a day and then restart it. The seafoam will loosen up a lot of gunk and foul out the plugs.
These bikes are terriffic to ride when running right, but with any used bike, require a little TLC to keep them happy. You will find a ton of technical information here as well as helpful members! Welcome aboard!