Luthier
I've had my 1979 Darmah for eight years or so.
I only do about 3-5000ks a year on it and they are mostly on trips.
It runs in summer, 30deg plus and winter -10deg errr..less.
It has now got around 55,000ks on it.
I've had no major problems with it at all and it would be the last bike I would get rid of.
As far as regular complaints that you hear about are concerned;
Electrics - I've never had an issue with electrics and I've ridden it for four hours in torrential rain, left it parked overnight in a paddock with 12 deg frosts or rain.
The closest I've had was due to my own hands of processed pork. I removed the pickup backing plate which needs a special jig to re-position.
The electrics on the Darmah were supposed to be the first really reliable example produced by Ducati (but that's really because they outsourced them!).
The leads on the pickups are deteriorated but I simply sleeved them and put them back, they have kept on going.
The grommet from which the pickup leads emerge does weep a bit but not enough to be worried about - I'll look at it one day.
Cush-drive - my cush drive looks like it has already been drilled and re-bolted.
Starter motor - the sprag clutch on these is supposed be liable to collapse. I don't dispute this but I've had no problem. I think I read somewhere that a 916 clutch fits?
Big-end - this is the thing that I'm most careful of. I run a 50weight mineral oil and change it every 1,000ks and filter every second change.
Possibly over the top but cheap insurance I figure.
I met a bloke at a rally once who had a Darmah with 114,000ks on it. He claimed that it had never been re-built, he never warmed it up (I can vouch for that, I saw him in the morning and he just cranked it and was gone) and only changed the oil every 10,000 ks or so.
The only time it has let me down is when the gear selector mechanism fell to bits but this is a known problem and is easily fixed by anyone with a bit of mechanical aptitude.
The shims aren't difficult to do.
Ummm what else....the chain chews out the rear of the crankcase if it gets loose so look for that, I don't know if it really causes any problem though.
The neutral and stand lights probably won't be operating. You'll never select neutral when the engine's running unless you're still moving anyway and even then it's a big dose of luck.
The mainshaft seal can start leaking but you can easily fit two or three seals over the shaft to fix that.
I replaced the head bearings early on.
The swingarm bearing gets loose and worn unless regularly greased, I understand that they are hard to get replacements for.
That's about it really.
Definitely a worthy bike as far as I'm concerned.
Good luck.
Ian