My GS500 97 has just about done 90 000ks. I don't know what the service history is and suspect that most parts are the original. I don't think the bottom or top have had any work done at all except maybe a 20 000 service. I was wondering what components might start failing me. Ive rebuilt the clutch and front suspension, front and back calipers as they failed

I am experiencing a loss of power (Hopefully just a large amount of crap in the carbies). But more of a worry my bike sporadically finds a false neutral and gets clunky changing gears, I put new plates and springs but haven't got around to doing the cable (I hoping thats the problem)

Does anyone know what else may start failing at this kind of age. 

False neutral. Yeah, I used to get them until I changed to a slightly different oil. I now use Motul 5100 and I think I've had maybe 2 false neutrals in the last 15,000 clicks. Also, it made the gears less clunky too.

Michael

What kind of service you perform really depends on what this bike means to you, and how big a problem it would be to break down on the side of the road.

In your position I would for sure:

1. Replace all of the brake lines.
2. Perform a valve adjustment.
3. Check the camshaft bearing clearance.
4. Rebuild the brake calipers.
5. Check all your bearings (wheel, swing-arm pivot, and steering stem) and repack
6. Replace the fuel lines.
7. Replace all vacuum lines.
8. Check the rubber bits of your intake system for cracks.
9. Check all bolts for torque.
10. Rebuild the carbs.
11. Check your brake rotors for run-out, and thickness.
12. Check your oil pressure.

If you want to get more intense... Split the cases:

1. Check your crankshaft clearance
2. Check your shift forks for wear
3. Replace your balance shaft bearings

To be honest, the last 3 items probably aren't worth it for a street bike. Ride it till it fails, and then drop in a new engine.

Thanks for the comments i think Burning one might be right with that list, though I was hoping for some advice that didnt mean as much work but it needs to be done.; I did a quick torque check today and found that my side stand was on the verge of falling off ! and the rear fenders has two bolts left.

You don't have to do it all in one sitting.

I've done everything on that list with my GS over the course of the past few months. Pick one or two items a weekend and do them.

Mmmmm, I've never replaced my brake lines, checked cam brg clearance, rebuilt brake calipers, replaced fuel lines, replaced vacuum lines, checked intake boots, checked bolt torque, rebuilt carbs, or checked oil pressure and do agree engine replacement is the practical answer to the last three items listed by burning1.

You have 90k km which is about 56k miles?  I put 80k miles on my 97 GS and did the required brake pads, chains and frt sprockets, oil/filter/plug changes, replaced clutch/throttle/choke cables at 50-60k miles, and put in Progressive springs and new fork seals around 50k miles.  I ran the exhaust valves with min clearance for a long time and one of them was down to a 215 min shim at 80k miles as they receeded into the seats.

My 02 GS is close to 80k miles now and never ran better.  Discovered more exhaust valve clearance stopped the receeding valve problem and expect them to go to 100k miles now with mid size shims, just check them every 10k miles.  Had a tight valve bucket that caused an exhaust valve to stick open and break at 21k miles, repaired engine, and have had almost 60k trouble free engine miles since.  Replaced one leaking fork seal around 60k miles.  One unusal thing was replacing all the wheel brgs on the 02 GS, two rear were damaged because a spacer was left out during a tire change and one of the fronts wore loose and I replaced both.  GS has sealed wheel brgs that don't require repacking.  And of course all the usual maintenance things done to the 97 were done to the 02.  Oil, brakes, chains, etc, etc.

If it needs fixed I fix it and if it ain't broke I don't fix it.  If you don't mess with the carbs they won't mess with you, keep them clean by using them.   

Thanks for reminding me. The OP should probably replace the fork oil and seals, check the brake rotor thickness, and inspect all the control cables. If it were me, I'd also replace the rear shock with an inexpensive aftermarket unit (or a Kat 600 shock,) clean the carbs, and replace the Cam Chain Tensioner.

I had an 86 Camry with 200,000 miles on the odometer. I drove around on 4 blown shocks for a couple years. You *can* ignore this stuff - most bikes will make it to 100K with nothing more than the occasional valve adjustment and oil change. That doesn't mean you should. Most of the stuff on this list will impact the performance of the bike. A few items are important for safety. Others will provide early indications of the overall condition of the engine.

Most of this stuff can be performed as part of routine maintenance... E.g. I'd inspect the camshaft bearing clearance, and replace the fuel and lines as part of a valve adjustment. I'd do the brake lines as part of the annual fluid flush and fill, and rebuild the calipers the next time the brake pads are due for replacement.

I wouldn't do all of this in one weekend, except as preparation for a track day or long trip.