it's underneath the gas tank.
The spark plug is located under the fuel tank. You need to remove the tank to replace the plug.
.7-.8mm
.6mm or 23/1000's
.028" is what most race shops go with.
No Spark
Spark plug is under gas tank. you must remove gas tank then pull coil pack off top of plug. plug is way down in head. you need plug socket and extension to get it.
.035
.028-.031 in.
GAP .030"
for the NGK plug # 2411 it calls for a gap of .032
It is located on the frame below your left foot.
how do you know if your yamaha atv is a 400 or a 450