Me & my buddy tried to run up Nikolai Creek a couple days ago. Not sure how far one can go anyway but for those who may want to try... Bring a chainsaw. We encountered a log jam after the 3rd (or so) turn and had to come off step and turn around. This caused my intake to suck vegetation; we were able to limp back to the Kasilof and lift the motor so I could lean out & clear all the trash out.

Anyhow, if it's actually worth running a jet up this and you plan to do it, bring a chainsaw.