when i ventured into my first real big 4 stroke dirtbikes i bought a 1984 yamaha xt250. well it had real bad compression and smoked. and i figured rings and was right need new rings so i tore down the motor over the summer and am just now receiving my rings and just saw that i didnt mark the cam's when at tdc. is there a way to figure out what position the cam needs to be at tdc ?