Imparticularly from 1991 to 2001. Thanks in advance.

The GS is a very reliable bike.  Only a few problems to watch for:

1.  Fuel starvation -- under some conditions (worn petcock diaphragm, or low engine vacuum for whatever reason) the stock vacuum-operated petcock doesn't allow enough fuel to flow to the carbs for highway operation.  Search "fuel starvation" on this forum for workarounds or solutions.  I just downshift (increases vacuum) or lighten up on the throttle (also increases vacuum), or if I want to go fast and not mess with it, turn the petcock to PRI.

2.  Some people swear the carbs are jetted too lean for optimum performance, but this varies with your local elevation.  I live at 1600 ft. above sea level and I'm happy with stock jetting. Others like bigger jets.

3.  Normal maintenance issues -- keep the chain lubed and adjusted and keep the valves adjusted on schedule.

4.  Depending on how the bike was treated before you got it, the fuel tank may need treatment for internal rust.  This is true of any older bike.

What kind of treatment takes place? How much does something like that cost?

Rust treatment, should your tank need it, is a do-it-yourself job.  Kreem is one product, I can't remember the name of the other common one.  It's a two-step procedure and the goal is to seal the inside of the tank and any rusty scale with it.  Mine didn't need it, so I'm not much help here on cost.

Search "Kreem" or "tank rust" and you should find what you need.

POR-15 is the other tank sealant. Most prefer this one over Kreem.

Check the oil on a regular basis. Air cooled engines use more oil.

Tank sealant covers surface rust and arrests the rusting process before it becomes terminal. Ie, you shine a flaslhight in your tank and it looks rusty. If your tank leaks, I would not bet on it. Of course you have to do it right, else it is a worse problem than you started with. Ideally, it buys time for you to find a tank off a newish bike that someone is parting out, maybe with a small dent to lower the price. When I've done it, I have also stripped the paint, dried it with a heat gun, resprayed it with a rattlecan, etc. Figure on a week to clean it out, coat and respray, with another month for the respray to properly dry. Done both POR15 and Kreem on various tanks. Took me a couple tanks of mistakes to realize that fast is not the way to go. You need some sort of garage to work in. It is messy and smelly. I am looking for a cheap tank to do in Rhinohide (bedliner) for that streetfighter look (just for fun).

This will help eliminate fuel starvation and petcock problems. http://gstwins.com/gsboard/index.php?topic=19363.0

Wow ok, thanks. How easy is that to do?

Quote from: SecondsFromTheFall on April 06, 2008, 02:50:13 PM
Wow ok, thanks. How easy is that to do?

Not hard at all.Just remember to block off the vacuum part and the prime part.When you disassemble it, you will better understand how the fuel flows when the knob/lever/selector is in a certain position.You basicly are turning the PRIme position into an off and eliminating the vacuum on.You already understand that.Took about 45 minutes my first time.I have another one that I am going to do.I had problems with my first one leaking.I think I got a little epoxy on the sealing surface.

fueling fueling fueling. oh, and fuel too.

carbs are sensitive to humidity, barometric pressure, butterfly farts and everything from a-z.

other than that, it's a great buncha fun. today it runs fine, tomorrow is coughs a little, the next day it scorches the road with smooth power. got me, every ride is different and usually fun.

The GS is one of the most reliable least maintenance required bikes and thus one of the most loved.  Dollar for mile you can't go wrong.  These bikes are so inexpensive and so trustworthy.  Few bikes can offer such cheap thrills.  Parts are easy to find also.

Thats what I've been hearing. While I'm saving up money I'll have plaenty of time to do my homework. I sat down on a brand new one at the dealership(and a ninja, and a Katana, and an SV640, and a GSX-R600 to humor the salesman) I liked the way the Ninja felt because it sat lower, all the other ones just intimidated the hell out of me, but sitting down on the GS I felt like the two of us could have some exciting times ahead.

Quote from: ben2go on April 06, 2008, 02:58:28 PM

Quote from: SecondsFromTheFall on April 06, 2008, 02:50:13 PM
Wow ok, thanks. How easy is that to do?

Not hard at all.Just remember to block off the vacuum part and the prime part.When you disassemble it, you will better understand how the fuel flows when the knob/lever/selector is in a certain position.You basicly are turning the PRIme position into an off and eliminating the vacuum on.You already understand that.Took about 45 minutes my first time.I have another one that I am going to do.I had problems with my first one leaking.I think I got a little epoxy on the sealing surface.

The only problem with this modification is that you'll have to remember to shut off the petcock every time you park.  I like the "automatic" nature of the stock petcock, even with its known problems.

Quote from: trumpetguy on April 06, 2008, 06:20:21 PM

Quote from: ben2go on April 06, 2008, 02:58:28 PM

Quote from: SecondsFromTheFall on April 06, 2008, 02:50:13 PM
Wow ok, thanks. How easy is that to do?

Not hard at all.Just remember to block off the vacuum part and the prime part.When you disassemble it, you will better understand how the fuel flows when the knob/lever/selector is in a certain position.You basicly are turning the PRIme position into an off and eliminating the vacuum on.You already understand that.Took about 45 minutes my first time.I have another one that I am going to do.I had problems with my first one leaking.I think I got a little epoxy on the sealing surface.

The only problem with this modification is that you'll have to remember to shut off the petcock every time you park. 
...

Not completely true. If the float needles seat good you will not have a problem.
My track bike never leaked fuel and it did not have a selector valve.