I've got a 650 on the front of one of my bikes which has a 700c fork. Yes, this was for barspins, so ****off.

It is annoyingly unstable at low speeds, so if I'm going for an actual ride it gets a 700 thrown on. If I'm ****ing around at a park or whatever, it gets the 650.

All in all, if this is for barspins, which I assume it is, go for it. If not, then there are much better ways to make your bike fit better.