my brother got one when i was 4 or 5.
not the best experience i had when i was a little kid, my dad started it in the snowmobile trailer and it was so loud i got scared and cried lol (true story)
anyways, good quads, indestructible (trust me, my bro and i are good at that sh*t)
one thing i say to check, is the case by the front sprocket. i just say this because we threw 2 chains into ours.
the first just had a little crack that leaked, the second put a nasty hole in it.
if dirty, clean it off with your finger and look at it (not sure how accessible it is)
but check for cracks or JB weld or anything that shouldnt be there. cases are hard to find for these