Motorcycle Repair: fork oil, yamaha Vstar, yamaha vstar 650, couple pints

Question
I have a Yamaha Vstar 650, to temporarily staunch leaking of a fork seal I had added a heavier weight oil, which I am now changing out.  Of course manuals all just say "use 10w yamaha fork oil".  Our Yamaha dealership is a new emerging piracy, I mean what they want for a couple pints of fork oil is outrageous!! My question is; Is fork oil a totally unique item, or can I safely use say, just a nondetergent 10w oil off the shelf? (the only straight weight 10w I could find is nondetergent).  Will adding a bit of transmission fluid stop leak hurt anything?  I'm hoping it may slow my leaking seal until this fall.  It's barely leaking as it is right now.  Thanks, Blue.

Answer
Fork oul has an additive that eliminates frothing, frothing is oil that once agitated gets full of air bubbles, the air bubbles in the oil will cause the damper assy. orifices in the forks to not work, there will be little or no damping. Use fork oil.