Hi, Making good progress on the K100 5/86 RS. It now finally runs. Thanks for the assistance. 
Which brings me to the front end, The next challenge - the Disc rotors are under spec. & the upper section of the front forks look bent [as best i can check visually while still mounted] 
Is the fork/s fixable, do you have to buy one or a pair ?  Are other models interchangeable ? 
Are the bolt on rotors advisable or is the complete unit best to buy [hope iv'e explained it ok]
Looking forward to any help or guidance 
Cheers   Dale

Buying a complete rotor and carrier will be more expensive. You'll find they probably come bolted anyway.
Bolting is ok. Make sure you get the SS bolts and nyloc nuts with the rotor.
Its easy to change over although some say it takes a bit of effort to get the old rivets out, just cut the flats off with a 4" cutting disc (rotor side so you dont damage the carrier). Only took me about 15 mins.
Install nyloc nuts to the inside

Ebay
MotoHansa - Sydney (pricey)
Show n Go - Adelaide (ok prices)
Munich Motorcycles - Perth

As regards the discs, if you can live with cleaning the wheel once a week or so I'd go with cast iron rotors because they're better braking material. The downside is they do drip rust in the rain and the wheels don't like it.

Are you sure the stanchions are bent? I suspect you're (hopefully) suffering from an optical illusion. Was the bike in an accident? If you're talking about the run between the top and bottom yokes then the headstock will be damaged and the frame will be a write-off, but equally I'd say that if you can see damage in that area then you'd see the damage to the bottom of the headstock too.

You need to drop the forks out and put a known accurate straightedge against them (a spanky new builders spirit level will do the job if you think you can see a bend). Minor damage can be rolled out with specialist equipment but truthfully, I suspect that a set of forks from ebay or a pair of stanchions from BMW would be cheaper (and safer) than the repair route.

My experience of checking and repairing front ends all revolves around Moto Guzzis, so someone here may have better knowledge about Ks.

good to hear you moving along with it Dale.

If you're forks are bent, I'll have a set from an 86 K100RT available shortly.  I haven't picked up the bike yet(hopefully this weekend), but it's going to be fitted with a K1100 front end I have laying around so the forks will then be excess to requirements.  The disks might be good ones too, I've no idea till I pick it up.

Whereabouts are you in the mountains? I'm in Mt Riv.

Al

Thanks Dai for the questions. Went and did some checking.
   Background is the bike had a slide down the road - why? don't know.
The previous owner bought it in this condition several yrs ago - now lost interest.
   The fairing is badly ground away on R/H side. The wheel & tire show no evidence of a severe impact.

Looking at the bike from the front - 
   The R/H disc sits in the center of its caliper But the L/H disc touches the R/H side of its caliper.
Undoing the bolts in the yokes for the L/H stanchion & bottom of the L/H fork and then rotate the stanchion 120*  the brake caliper moves position so the disc now sits in the center of its caliper.

   Moving from the front of the bike to the R/H side and view the stanchions side-on they are parallel from the top yoke to the lower yoke,  but as you look down the stanchions the far one bends to the rear of the bike.
   Also, to remove the front axle required some force.

I'll check out those contacts Kapt'n

Al - thanks for the offer. Because of the above, i think the forks are bent and so i would like to see if your forks will suit.
I'm in Katoomba and don't mind dropping down when convenient .

Cheers