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Old 04-30-2013, 02:56 PM   #7
disston
ShadeTreeExpert
 
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Joined: Mar 2011
Location: Silver Spring, Md
Oddometer: 8,181
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?
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