Join Date: Jun 2001
Location: North Phoenix, Az
On my zx-7r, they call for 5W. I have experimented with weights, and settled on 10W for the track, 7.5W for the street (50/50 mix of 5 and 10W).
You may want to go to a heavier oil for the track, I can't see going to a lighter weight, unless that particular fork really runs better on lighter oil.
Best bet, stay with the stock weight, untill you reach the end of the fork adjustment.