I think that there are no differences in the cylinder heads and combustion chambers from 1957 thru 1985 that would have been done to accomodate unleaded fuel. Most guys replace the original seats with hardened seats, but usually when other head work is already being done, and that resolves the issue.

And is there really an issue? Some guys report running there IronHead since new on unleaded with no problems.

But i wonder how many miles a year they do. I, for example, ride about 15000 miles per year. Some guys take 15 years to ride that far.

 

Yeah, I probably fall close to that tree. Over my 20 years of Ironhead ownership, I've averaged a little over 2000 miles a year on mine, since I can't really ride it to work (I need to have a car available), and have lots of other weekend "irons in the fire". I have been riding it a lot more the past couple years, though. Still, I've put about 40,000 miles on it with no problems, adjusting the valves as needed, and it already had about 9,000 on it when I bought it.

 

i have an original 1985 owners manual for my ironhead and it says to use 89 octane or higher leaded gasoline. doesnt mention unleaded at all so i dont think either it or the service manual are misprinted. you can buy lead substitute/additive at about any auto parts store thats what im gonna do!!

 

My money is on the Sporties from that era not running well on unleaded, rather than anything else. They have poor combustion chamber shape and poor porting as stock. Other brands had similar problems around that time, so it was not unusual.

There is a current question in the Sporty forum about twin plug heads on a recently purchased iron head. That was one way of improving combustion when tuning, even on pushrod BMW twins!

 

I've been working on a 79 shovel low rider, and before I started it the first time, I drained what gas was in the tank, and put what I had for the lawnmower in the tank...probably the cheapest, lowest octane stuff I could find at the time... the engine started, and idles ok... but run a little rough... this could be the low octane gas?... and do all owners of pre-80ish bikes use premium gas now? Can I add premium to whats in there, or do I need to drain it again? sorry for so many questions.... Thanks in advance!

 

Hi from the UK and welcome to HDF. Just top it up with a better grade of gas. They didn't need anything special in their day (I owned one from new), in the way of gas, just don't use the cheapest stuff. When running unleaded, which most modern fuel is, be aware the valve seats and possibly the valves themselves may suffer over time. If they do you should be able to buy modern replacement seats and valves that get around that problem.

 

Thank you for the reply... I think I'll just go ahead and drain whats
in there, and put it in the lawnmower. I'll go with the premium and
see what happens.
Thanks again!

 

Speaking of gas, I've been running non-ethanol gas in my Ironhead since late last year, and I swear that it runs better...quicker throttle response, and a little more power. It's not easy to find, though.

 

http://pure-gas.org/