I have my original owner's manual, downloaded the service manual from tech library, checked Torque Specs from Tech Library.  There is a general chart for torque specs based on bolt size (with a reference to cylinder head bolts).  Also searched internet.  I'm thinking the general specs listed in the service manual are too high for the fork tubes?  I found a chart that MarkT provided for an XT250, would those be the same?

The 1974 Service Manual has better specs... I'd use that if the earlier manual doesn't show anything...

Note that often Yamaha gave torque specs in the body of the manual where the describe the repair... and sometimes not all torque specs are in a chart. The later manuals are much better with torque specs.