Just bought it for my son for Christmas. After riding it for a couple hours then it went dead. I noticed some thick black sludge looking oil coming from the exhaust and then tried to crank it and the kick starter was seized up. I then remembered that I forgot to add oil after draining it the night before. I am still sick about it and yes I know how stupid that was. I feel bad enough so please keep all comments on that matter to yourself for now. What do I do now? Please dont say buy a new bike or new motor? Any help will be much appreciated. Yes I am an idoit.....

It happens to the best of us. hopefully it is minimal damage

it sounds like the engine seized , although this does not seem to be related to the sludge coming out of the exhaust .

you said you forgot to add oil. what oil did you forget, pre-mix or transmission ?

transmission oil. I drained it to put new oil in and forgot to add it back.

well then I guess I was wrong the "sludge" could be a result of the engine/transmission heating up. I cannot give any advice other than you need to have someone tear it down probably completely.

preliminary examination by a mechanic may give more info . I'm not real familiar with the probable damage in this exact scenario.

like I said though this happens to the best of us , hope it turns out to be the cheapest and easiest fix possible .