I have a 2001 trx 90. I went to change the oil and pulled the plug on the left (when you are sitting on it) instead of the plug on the right (oil plug). A little bit of oil came out. It wasn't much. I was wondering what this plug is for and what kind of oil to replace it with. There is a little red plastic plug on the top of the enging. It looks like this would be where you put the oil (that I drained). There is nothing mentioned about this in the manual. I dont want to tear up the kids bike. Any thoughts?

 

The one you pulled out holds the spring for the cam chain adj. just put it back in no harm done.
Oil fill is on the right side (clutch cover) to the back. Takes a little less than a Qt. use 10w40 JASO oil do not use synthetic oil the motor. The motor will not get hot enough to beable to turn the choke off.