You'd want to drop to a lower needle clip position first (richer) and see how that works for you. If it isn't enough, reference the Rotax Main Jet Correction Chart to calculate the proper jet. Given the temps you've mentioned you would probably go up about 3% in size. If you were running the stock .165's it would put you at a .170 from the available choices. It's pretty much based on keeping your mid range EGT's in check at around 1100 to 1150 F.