I said I thought there was a correlation between engine size and jet sizes. I was looking at the info wrong I think. There seems to be a correlation between age and jet size. The older bikes are jetted richer. But then on reflection I don't think it's the age but the compression ratio. The higher compression bikes seem to have bigger jets.
SS does much more rejetting of Airhead carbs than I do so I appreciate his input.
The later bikes also had leaner jets because of emission concerns.
This whole subject is very confusing because of the numerous variations BMW used. I just spent an hour trying to find the part numbers for every main jet BMW ever used on the Airheads. There are 14 main jet sizes. There are 5 needle jet sizes. At least 2 idle jet sizes. (These numbers are for machines sold in N America. There are some other sizes for European machines)
Anybody want me to type up the list for reference?