I have not found a lot of answers here but a lot of questions or statements. As far as oil goes, I put a blend in my 81 750-4 LTD and so far have not had an issue with it. I did notice a very small stain where apparently the head gasket is starting to leak slightly but I doubt it has anything to do with the oil I used. It is a 34 year old motorcycle with 32 thousand miles on it so things like this are expected. Finding parts seems to he more of a challenge than fixing problems. I was able to locate a head gasket but have no plans to change it until this years riding season is over with (Mid November). The motor seems tight and does not make any noise so I am not going to worry about a rebuild until signs point to it being needed (noises in the motor). I did see a post earlier that I found troubling concerning one of these bikes breaking a timing chain and destroying the valve train. I have looked in my manual and it does not speak of timing chain maintenance or when it should be replaced. If anyone knows the answer to this it would be greatly appreciated.