I think the manufacture states 6300 as "redline"- to be taken with a grain of salt.

I know a lot of folks say that 35mph is about tops with a 44T, I have run one of my bikes up to 43-5 with a 44T with two different cars used as "pace cars". The engine is still running.

__________________
If it ain't broke, and you mess with it long enough, it will be.