If you're a big 115kg+ guy taking on an average 60kg chimp, sure you could damage it enough to get it off you before it tears your face off. You'd still be far worse off than the chimp. Maybe if you were a 160kg+ strongman, you could simply pick the chimp up and smash it against the ground repeatedly or tear its limbs off.
Now if its a very large alpha chimp (90kg+) not even a strongman would stand a chance. That chimp would have arms more powerful than a strongman's legs.
No way.
A chimp spends most of its days swinging through trees. The grip strength on that thing would be incredible. There is absolutely no way that you are shrugging it off regardless of your mass or height.
What's gonna happen is that the chimp is gonna run at the man on all fours (we are not used to facing opponents that run this way). Your only real option is to maybe kick it back (if the chimp is within punching range it's too close and you're already fucked).
The chimp is then gonna leap through the air and grab a hold of you. How are you gonna defend that? Catch it out of the air? lol. Good luck. Most people are either gonna be dumb enough to stand their ground (chimp lands on your upper body/face) or instinct kicks in and you turn to run/shield yourself (chimp lands on your back/shoulders).
Using that incredible grip strength it'll be stuck to you like glue and within seconds it's gonna sink those giant fangs into your neck, face and back.
What the fuck you gonna do then? Thrash around screaming? Try and punch it? Where is your punching power coming from when you've got a fucking chimp attached to you? You think you're gonna land anything substantial on this beast while it sinks it's fangs into your body and tears your flesh/limbs off with its incredibly strong hands?
Sure, if a chimp just stood there staring at you, a full power roundhouse kick to the head/body would probably ward it off.
Good fucking luck landing that lol