Mike Moon

So I think it is a 1980 dt175g, the build date on the neck reads 11/79, the serial numbers is 3R9-004536. So what is it? Next, I need the schematic on the motor, cause of course it is not running, just did the top end. It had a mouse living in the air cleaner and it sucked all the bedding into the cylinder. But taking the side cover off the kick start side I have found a broken circlip I dont know where it is from and before ripping the whole motor apart schematics might help. Can anyone help with this? This is just a start to the rebuild/resto of this bike but need some help. Thanks Mike Moon