You want photography review or riding review? Both look great! A few nitpicks from a fellow photographer though, hope you don't mind:

First two are a bit flat, and slightly overexposed (see hotspot on shirt). Try bumping the contrast and color up a bit in PP. Also, I wouldn't have the log ride/rider centered in the frame, stick it over to one side (i'd pick right side due to the curve of the log ride). Good shots nonetheless.

The landscape is about 1/2 stop overexposed as well, sky is a bit too blown out, but color is better. Could still use some PP work to bump up the colors of the foreground. Not much you can do about the blown out sky now, just something to remember for the future Very nicely composed though.

Last shot, of the bike, is great. Colors are far far better than all the others, you have good blacks and its very sharp. Did you bump the colors at all in PP? There are some signs of compression as well, what do you use to compress for the internet?

This is what I mean for the first shot: