Hmm different cylinder to my problemo.
I had (and likely still have) a problem with the No.4 spark plug thread.
With the exception of the first service from new I've serviced my bike ever since.
At around 50,000 miles, which was in 2009 I serviced it and changed the plugs.
When I took the No.4 cylinder plug out, a copper washer came with it. The copper washer must have been located under the plug washer.
Now I'd done ever service apart from the first one, and I hadn't put it there, and I suspect they didn't change the plugs on the first service because it had only done either 1000km or a 1000 miles. And if they did change the plugs why stick an extra copper washer under one of them?
In any event having taken the old plug out, I tried to screw the new one in. No chance, none whatsoever.
I ended up re-tapping the plug hole with a old spark plug with grooves filed in the threads and all manner of aluminium shit came out as I did so.
Ultimately I managed to get a new plug in (an iridium one), and I decided not to change the plugs again.
Oddly enough, or not as the case maybe, the bike still runs o.k. and it's now six years and 30,000 miles later (it's now clocked 80,000 miles) and everything else is worn out anyway... so I guess it doesn't matter that much anymore.
As regards vac gauging your carbs, I've done it before for other Foccers, so why not you.
I'm still working (old bugger hanging on and trying to get to state pension age), so you'll have to give me a ring to see if I'm available.
The works no. is 01204 845382 and my mobile is 07813 439196.