I don't mind hiking or even jogging in full keto, but for me cycling is not fun when fully bonked. Cycling demands brief moments of high intensity that can be pretty taxing without some glycogen power. Some examples would be going over a little hill, taking off from a dead stop, or crossing the steep part of a switchback.
That said I'm not on a keto diet. I have done it on occasion though mostly to shake things up a bit. Obviously if you are completely used to it everything will be easier, but even then you will not be as fast as you would be on carbs.