Is there an Autolite spark plug that compares to a Champion J12Y spark plug? I would like to go with an Autolite plug if there is one which will work.
What type of plug would you suggest to run on an old Harley?
I did a search on Google and came up with this list from sparkplug-crossreference.com:
You'll need to actually see if any of these are a true fit or not.
As far as what to run, I don't think you've given enough information, or what problems you are currently facing or are trying to overcome. Also, a picture of your current spark plug would help in reading what the spark plug is doing. If it is black and you are seeking black smoke from your tail pipe, you may need a hotter plug (as well as some carb tuning). If it's ashen white, you may be too hot, so might need to go to a cooler plug. If it's just right in the middle (light tan color), the heat range is probably right on. As far as brand, I have never had any luck with Autolite, though people keep using them, so there must be something there.