Many thanks Frode, and especially Grant for your detailed advice. It's interesting that you say that bad timing can cause overheating - I think that's what caused the problem in the first place. Unknown to me, a tappet guide had broken. I guess this happened in Iran when I suddenly had to make a major adjustment to the timing - I thought it was just because the bolts holding down the rotating backplate of the points had come loose, and it had adjusted itself, but now I know that it's because a tappet was wobbling about.

Anyway, I haven't managed to sort out my problems. It was clear when the barrel come off again that the re-bore had been no good. It was done on a lathe, which I now know is a recipe for disaster - shame the mechanic had it done that way, particularly since he knew that there was a re-bore machine in the next town. Had it properly ground out there, and filed the piston as recommended, so it was looking rosy.

Back on the bike, it turned out that this wasn't the only problem. The last piston seizure had indeed felt particularly severe, and it seems that something in the crank assembly broke. I've been carefully considering all the options (including a kind offer to help in Istanbul, if I got the bike there, by an English guy contacted by the Istanbul HU community).

However, weighing up the costs and time implications, I have reached the difficult decision that it is better for me to abandon the bike. It's heart-wrenching, but I have to be back in England before too long, and even if I spent the several hundred dollars required to get the parts here, I'm still not convinced the bike could be fixed, and I would run into severe time troubles, having already spent over three weeks trying to sort it out.

I'm currently trying to persuade Turkish customs at the Iranian border to take my bike and relieve me of the need to leave the country with it (it's in my passport), which of course is easier said than done!

A sad end to what has been a great trip, but I'm sure there will be others.

James