It has been leaking oil out of what seems to be an overflow tube and out the drive shaft. Im thinking it might be an O ring but I'm not sure. Also, the front sprocket is very loose and I have no idea how to tighten it.
Thanks

 

Bump

 

You say its leaking out the overflow tube. Your not overfilled are you? What do you mean driveshaft are you talking about the shaft the sprocket is on if its leaking here. It would be a seal. And the sprocket is held in place with the washer that should be bent up the sides of the nut. Take a flat head screw driver and hammer and flatten the washer back out and turn the nut. But it should not be real tight hand tight only then bend washer back up so nut cant turn.

 

Yes I'm talking about the shaft with the front sprocket on it. How do you tell how much oil to put in it? And where would the seal be that I need to replace?

Thanks

 

That seal behind the sprocket is notorious for leaking on the DRZ400 I check mine all the time. Oil will leak on your boot it will leak quick and smoke your motor if you dont watch out.

Good news is that it is cheap and you can do it yourself. It goes in from the outside. Remove the sprocket circle clips and carefully pry it out with damaging the surrounding area.

Heres an idea. Buy the owner manual or download it off line.