Sorry I missed the requirement to submit an introduction so here it is. I’m a 50 something who used to have a K100RS in the 1990s when I lived in Australia. I’ve since owned Ducati, Rudge and MV Augusta and more recently a R100S. I’m now looking to re-enter the K series world and hoping to find a well looked after black 1985-86 K100RS. Mileage less important than condition.  
I’m based in the Yorkshire Dales and like to travel south without the hassle of being stuck in traffic!
James

WelKome James your not the first make that cockup 

Welcome James

Hiya James,

50 something here too and I stupidly sold a black K100RS - THREE TIMES! My current 16v (black of course) is staying with me until I'm too old to ride it.

One will come up and even if it aint black - it can be made so 

Bonzo wrote:Hiya James,

50 something here too and I stupidly sold a black K100RS - THREE TIMES! My current 16v (black of course) is staying with me until I'm too old to ride it.

One will come up and even if it aint black - it can be made so 

12 MONTHS ROAD TAX WILL SEE YOU OUT THEN BONZO

Never had the experience of selling a K. Never done it.

Good thing these days is €26 annual road tax and €30 annual insurance every time I get another......

Realised yesterday...1,800 miles in last 3 months.... usually I go through a set of tyres but its getting to be a struggle to use a tank of petrol and trying to get the idea of oil changes at time intervals instead of mileage.

Welcome james from down under, the land of sunshine and great roads, hope you find your K.
Cheers Mike

Thank you all for your welcome, it’s very heartening!
I may have found a K. Wring colour but not offensive and 1989 rather than ‘86-‘87 but it’s not a million miles away. I know about the water pump/oil pump gasket failure problem to look for but would welcome hints as to things to ask the owner.
I’ve asked for a compression test and numbers of owners etc but all hints gratefully received.
J
Keep well all!
J

My view: it's hard to say with a K - spares are plentiful and cheap enough and there's nothing that can't be fixed - so long as the price is right. 
The 'stuff to watch for'? For me it'd be the tank. Leaks underneath the tank - a small leak can show as just yellowed discoloured paint on the seams underneath the tank and around the front LH outlet & return pipes. Tanks can also corrode at the very front seams near the headstock. Pinholes might just look like small bubbles in the paint - corrosion might have been filled and overpainted. Badly painted/dented tanks are common too - the fairing can crease the side of the tank if the bike has ever fallen over. None of this a problem as the tank (like everything else) is an easy swap. The reason I mention it is because a decent tank costs a few quid, and then there's the cost of paint if cosmetics are important.
My two penneth 

Based on what had to do to mine, over and above normal service items:

• Clutch - that stupid o-ring on the output shaft does not survive 30 years
  
• Radiator - need a decent test ride to get up to temperature and pressure
  
• Brakes - corrode when left standing
  
• Discs - they do have a wear limit
  
• ABS - nice to have but too expensive to repair
  

My RS is a 16V in 670 black metallic. It's going to get resprayed to someting a bit more colourful. While not showroom, the current paint is decent enough. I also have an RS fairing from and 8V in flat black. If you heart is set on black we could perhaps arrange a body swap.

Thank you, those are helpful hints of which I shall take note!

Look for leakage at the oil/coolant combination pump weep hole and the transmission/intermediate housing weep hole. If leaks at those places aren't pooling on the pavement then you're likely to have some trouble-free riding for a while. Leaks at the transmission weep hole likely mean a leaking output shaft o-ring, leaking shaft seal, or both. If the clutch isn't slipping and the moto isn't broadcasting an oil slick like a depth-charged submarine, you've got some time to enjoy the ride—likewise with the combo pump seal leak. In either case, the piper will be paid eventually. The combo pump seal repair can reveal a worn oil gear that must be replace and a coolant impeller that might need replacement too. The o-ring/main seal replacement is just nut-and-bolt grunt work but, if you're the obsessive type, you might find other parts on the way in that could be replaced to ease a troubled mind. 

You can tell from the feedback that you have found the home of K lovers. Unfortunately not all owners are like that, so watch out for poor/outside storage which can lead to a lot of degraded rubber and plastic - coolant hoses; fuel and breather pipes; TB manifolds; the little nobbly caps on the TBs etc. All readily available from spares, but these bikes don’t like air leaks. Enjoy.

This post just to thank you all for your advice. Currently working around COVID restrictions so the vendor and I have agreed to wait until March when I may be able to view it. It’s not MOT’d and the last MOT was six years ago and the only comment was ‘light misting of stanchion on front shock absorber’. I’ll make a note of your advice and thank you for the offer of a fairing swap too, that might be of interest...

Hello all, I’ve posted on the tech forum about the compression tests the vendor has done. All comments welcome. 
J

  James P

consider that there are several differences between early K bikes and the ‘86 and later k’s
all in all I have had great luck with my bricks.
ride safe.