Dear All
I would be very grateful if you could take a look at my problem and let me know what you think.
***For the short version, just go straight to the bottom of the message, I know you're all busy people

I bought a 1980 R65 18 months ago, bad idea, it has had loads of problems. To cut a long story short, it was in the garage for most of last year, while the mechanic fixed / checked a lot of things: cleaned the carbs, checked the cylinders, redid the wiring / electrics....$$$
Anyway the guy fixed it up and the bike ran fine until a couple of weeks ago. Until then, the engine never started great, would cut out if you werent careful, but ran fine once warmed up after 5-10min. Then on cold mornings (Barcelona cold = 5 Centrigade or so), the engine began to start but only with the choke, and making a kind of muffled weird engine noise, with not enough power to actually ride, and would cut out as soon as you took of the choke.
***Then last week, when I started her, the starter couldnt turn at all for a few tries, until eventually it started and oil spluttered out of the joint of the right exhaust pipe. I always noticed that this side produced a little black smoke while running, compared to the left. Since then I haven't run the bike for fear of doing some serious damage.
See photo attached.
Any idea what the problem could be? Is this something serious?
I already spent a fortune on this bike with the mechanics

Thanks a lot for your advice!!
Rory