I'm sure most have seen this on Yamaha it website but if not it's a god read.
Bobby Ratliff shared a link to the group: Enduro Yamaha IT Series.
I had my ragged 490 up to 95 mph. I'm sure if I went up one on the front sprocket that it would do 100. Although without some balancing and tuning it's not some where you want to be for long.. Lots of Vibration. I had a speeo from a XT600 I had tie wrapped on to the cross bar. My eyes were bouncing around in the sockets fro the vibration.
Great read. I have the 490L, the motor is bullet proof. I wish we could have a modern versions of the IT, 2 stroke and all. Yamaha would sell a ton of them. This bike will climb anything.