Thanks for your reply – turns out it was an iffy coil. I replaced the coil and condenser and it’s been running really well for the last 2000 miles. No more misfiring or stopping when it gets hot either! I’m not too sure what I expected from a coil which must have been sitting in the rain for a decade!
In the end I ‘splashed out’ and bought a new condenser and genuine coil from the MZ shop. Coil was slightly deerer than the ones from germany or on ebay, but I’ve had no issues at all, and it’s turned out to be a bargain. Condenser and coil was around £40 posted, money well spent.
Plus it arrived in a few days, so the bike wasn’t off the road for hardly any time at all.
I can’t blame the condensers, but to answer your question, the condensers were from either Ost2Rad or ebay. I can’t remember. They’re probably O.K – it’s just they (like any other condenser) wont like an iffy coil!
I had the same issue – the condensor would last 30 miles, and then the bike would start misfiring when coming up to junctions. Often stopping. Check with another coil, but a good coil, don’t make the same mistake I did!