Fouling Plugs and Hard Starting

[YZRIDER1127]

I have a 04 yz450 and about every month or so my bike starts to get really hard to start. Then it gets to the point will it will not start and i foul out a plug. Any reasons or suggestions i can do. I read on a motoman393's web-site that you can remove a light blue wire but that was on 426's.

[bluerider450]

my bike gets the same way but maybe around every 2 months i still going with jetting but im not sure