Grinding sound from 4 stroke motor

[Eddie7799]

So I have the 79cc 4 stroke motor from gasbike.net, I just got done installing the whole kit on my bike and after a couple minutes of running, it makes a horrible grinding sound within the engine and it dies, also when I give it gas it makes the sound and then dies. But still turns on and stuff. Any solutions? Is my engine broken? Another question, what kind of oil does the engine require? I have it running on SAE 15W-40 as what it said on the little tag when it came in