1988 K100 RT - what other surprises?

OK so I've just inherited a K100 RT from 1988. It's not had much use in the last 3 years and has basically been stood for the last 12-18 months.

It had a big overhaul just beforehand so has new pads, rear shock tyres etc but I've had a couple of nasty and expensive surprises. The first being a knackered fuel pump as the petrol had done for the rubber seals and had killed the pump.

The next one was the slightly rubbish centre stand which snapped and caused mirror / screen / fairing damage.

I can see that the fork seals have gone and will need doing, but what else should I be looking for? Have I exhausted the 'known' weak points or is there something I can do pre-emptively?

Potentially:

Oil/water pump seal failure. It's an odd design being a combined water/oil pump, a consequence of taking a small car engine and turning it on its side. The first indication is a weep of oil from the tell-tale at the front of the sump pan. What looks like a fixing hole minus a hex-head screw. It can weep for years and never get worse. Keep an eye on the engine oil for signs of emulsification as when the seal goes properly tits-up oil and coolant may mix.

Rattles from the output-shaft cush-drive cup rivets. Item 10 below:



The earlier bikes (yours) have a six rivet fixing and the rivet holes can wear. Ultimately the rivets fail. The bits can't get into the bowels of the motor so the consensus opinion is to live with the rattle and fix it when or if it finally fails.

The above shouldn't be confused with a tinkling sound from the alternator drive which occurs if the cush-drive rubbers break up:



Less likely on the four cylinder bikes than the three's for some reason according to Steptoe but if left the take-up of drive can break the vanes:



Cheap and easy fix.

Spline failure, drive-shaft and or engine output-shaft. Simple to check the drive-shaft splines and to lube. The engine output splines require gearbox and clutch removal (best left until a clutch is needed).

Don't worry too much though, these old "Bricks" are very robust, easy to work on and pretty cheaply too. The electrics have a few oddities so if you have a problem with that it's best to do some research before you end-up wasting a lot of effort looking at the obvious things.

A K100RT isn't the most exciting of K-Series which in themselves are not particularly exciting. Their attraction is that they are good for hundreds of thousands of miles, will easily cope with modern traffic conditions and can still put a grin on your face. All the while they are cheap to run.

Everything Mike has said.
Plus the clutch arm/pushrod gaiter on the rear of the gearbox can split. If leaking replace straightaway as you'll find water will replace the gearbox oil.
Bastard of a job on the K100 models, but a 5 minute job on the K75 due to the exhaust allowing the clutch arm to be dropped furhter down allowing easy replacement. Plus the K75 silencer is held on with one decent sized clamp and slips off out of the way if needed.
And while you're doing that job you'll find the clutch arm is likely to be semi seized.