The problems mainly relate to slipped liners (common problem) - that required the new motor and was the cause of the LPG backfires. Ths liner slipping was due to manufacturing errors - the liners weren't pressed fully home when the engines were built.
I think it had the slipped liners from overheating due to a 2/3rds blocked radiator. By the time that was found, it was too late. I suspect it had slipped liners when I bought it. At that time, the problem wasn't as well known.
Ron

