I'm new here, but ive been using this forum for awhile to get information about my engines and such. I created this account to see if anyone could help me with my dilemma. I was riding my titanxc50s 4 stroke to school last thursday at about 20mph (i weigh 175) and all of a sudden i heard a loud buzzing noise and the piston seized up and the engine wouldnt turn over. I took it home and dismantled the entire thing and discovered that my exhaust valve was broken and had lodged itself in the combustion chamber. I'm not exactly sure on all the names of the specific parts, but if i had extra parts i could fix it. I havent found extra exhaust valve parts for this engine anywhere for sale on the internet. Any help would be greatly appreciated. I can post pictures later if someone wants to see what exactly broke.