I have a 1975 1000 cc ironblock sportster. ( just given to me ) Back in those days people burned leaded gas. Question is can I use unleaded or do I need to buy a fuel additive? Also should I be using the 93 octain like I use in my 07 softail.
Unless there is something I don't know about, I am pretty sure you mean Iron Head, all blocks ie cases are aluminum. Whatever, you engine was originally designed for leaded gas as the lead was used as a lubricant. I believe that unless the valve guides and possibly the seats are replaced you will need to use an appropriate additive. As far as 93 octane goes you need to know what your compression ratio and timing is.
I believe, and I am sure if I am wrong a few people will school my ignorant ass, that octane is used to slow the travel of the flame front. High compression or severely retarded engines need higher octane. You will know you don't have enough if it knocks. You also need less octane at higher elevations.
Enjoy your bike, make sure to let us know the first time you hyper-extend your knee. We will give you plenty of commiseration.
I would run the highest octane i could get there is so much crap in fuel nowadays you need the high octane to burn all that crap (ethanol).I even use octane booster addative.
so youll have one leg bigger than the other great for kickin ass.lol
My 74 1000 runs best on low octane, never put additives in it. I have a tendency to rebuild the engine about every other summer. But im extreamly hard on that little sob. but its a blast. You should be fine with regular pumpgas, no need for the octane boost.