I bought this motorcycle in non-running condition, but quickly found the problem... the previous owner attempted to replace a head gasket, and put the valve shims back in the wrong place. After switching them around, the bike ran great, and has been for quite some distance.
Let's face it, the stock brakes just plain suck. They may have worked well in 1983, but everybody I know complains about the "spongy lever" feeling. They don't exactly stop the bike too well either. No problem, the front fork from nearly any Suzuki from 250cc up to at least 850cc built during the '80s will drop right in. I replaced the entire front fork with one from an '84 GS550ES.
A 16 inch wheel (instead of 18 inch) makes steering the bike at speeds above 40mph much easier... I'd say it makes it into a completely different bike.
The dual front brakes with opposed piston calipers easily stop the bike faster than any car that may be tailgating you... be careful!
The hydraulic anti-dive system is a blessing as well. It turns a 3 to 4 inch brake dive into almost nothing. While the electric system on later models has some advantages, they both do the same thing.
Voila! 90% of the problems with the GS450 are solved with 100 bucks, and a free Saturday. Can't go wrong with that.
Although I haven't ridden it for long, I take it on long trips. However, I haven't ridden it that far either. I haven't had any problems with the bike that led me to major repair... nothing more than having to adjust the idle speed and clutch on occasion.
This may be a low-repair bike, but it's definitely high-maintenance. It requires frequent oil and filter changes, being every 1,500 miles mostly city driving, but can be held off to 3,000 miles if you take it really easy on long highway trips.
The clutch pushrod and cable needs to be checked and adjusted frequently; best to do that once a month.
The chain needs to be adjusted every 500 miles or less... seems like every time I stop for gas, I end up adjusting the damn chain. A racing chain would probably take care of that problem, but it won't clear the tire (I'll get to that later).
A "well known" problem for this bike is the regulator/rectifier going south. However, I feel that has more to do with the battery going dry, than faulty equipment. The battery will lose electrolyte quickly, keep it topped off!!
Another "problem" is the stator burning up. I heard about this when I got the bike, and decided to check it while I was working on the engine. It was covered with burned oil on the bottom, and fine at the top. Seems to me the engine oil is used to help keep the charging components cool, and most people don't check the oil level often enough. Since the stator is on the right side of the engine, I will not idle the bike on the side stand, it will let the oil drain away from it. I figure if the oil is kept clean and fresh, the stator won't accumulate burned oil on it, which is definitely a contributing factor to failure.
Although most people complain the bike has lame torque, I find it has plenty of power past 6K. It's fast enough to do anything a car can, and get 60+mpg too.
The rear suspension is outdated (obviously), and the twin shocks give no room for mounting saddlebags. With a grinder, and some clever welding, the full floater aluminum swingarm from the previously mentioned GS550 fits in there really nice. The adjustable preload and hydraulic disc brake are also a big plus. This leaves two bolts sticking out of the frame where saddlebag mounts can be fastened (with more bolts elsewhere, of course). It also makes room for a heavy-duty racing chain, which allows adjustment to be dealt with every oil change, not every fill-up.
All in all, I'd say it's a decent looking bike to begin with, it's too bad this model was only available in this country for one year (the 1983 model is WAY different from the previous years).
Suzuki obviously refused to even look at it, much less do any work to it (they won't even replace a tire for me). They are more than willing to sell me parts for it, they seem to have hordes of vintage parts stashed away somewhere.
I liked it when it was completely original, but upgrading key components made it so much better. It's a really easy bike to work on and tinker with. That makes it perfect in my book.