I'm curious about what parts will interchange with my 1975 Ironhead. I finally got the title back and I'm starting to work on it.
It's a true basketcase with some parts missing. Some parts damaged. It's completely tore down.
I eventually will rebuild the motor but I want to do it right and that takes money. Until then I was looking at either finding a parts bike to "help'' get it on the road quicker or buying used parts individually.
I know someone that has a 81 Ironhead motor, forks, and several boxes of other parts from the bike. Would the motor and forks work on my frame and my triple tree?
If not, can someone tell me what years I should be looking at that are direct fit? I haven't seen any 73 to 76 bikes within my price range as a parts bike. And I'm not exactly sure what parts interchange from 57 until evo. Like the forks, motor, rear hub, brakes...etc. (All things I'm in need of).
Thanks for any help or advice.

 

You will need to have the Factory Parts catalog[s] for reference as you go along. 99451-78B covers 1954 to 1978 and 99451-85A covers 1979 to 1985 [especially the -78B edition]. These catalogs list all of the parts and part numbers, and have schematic diagrams showing how the parts fit together.

The Factory Service manual 99848-78 covers all the procedures for 1970 to 1978. You will need this also.

The 1981 has a 15/16" fork stem while the 1975 has 7/8. Conversion neck cups are readily available that will easily allow you to install a complete 1981 front end on the 1975.

If it is just the forks then yes they will slide right in. Fortunately 1975 was the first year for the 35mm Showa forks, which were used right thru 1985.

Starting in 1977 the frame was changed on the bottom right frame rail. A flat spot was included to allow the oil pump to be removed with the engine still in the frame. So the 1981 engine may go into the frame but if the pump ever needs to be removed the engine will have to come out. You will need more info about this. It may not be a go or no-go issue.

The 1975 & 76 have a crude crossover linkage for the shifter and brake. Up to 74 all Sportsters were right side shift. The gov't mandated change. The full change did not come until 1977. So this also will be a problem that you will need to look into.

There may be issues with the way the rider footpegs install.

The rear brake system was essentially the same [but not exactly] from 1957 to 1978. 1979-on changed to rear disk brake.

Here is a booklet which may help, covers all of them including Sportsters....

What Fits What on HD Motorcycles 1936 to 1983
ISBN 0-933078-11-0
www.armanpublishing.com $12.00

Here's an IronHead Fitment Chart on my OneDrive [used to be SkyDrive] which may also be helpful ...
https://onedrive.live.com/edit.aspx?...pp=Excel&wdo=1

You have lots of research to do. This will be a fun project. All the best!

 

Thanks IronMick for the info. I have a long way to go but I'm set on fixing this bike up and putting it back on the road. If I can get the 81 parts cheap enough I will see what I can use and store the rest back for selling, swapping, or starting a new project.