fouled plugs

Good day All, I know what you're thinking- "oh geez, another I fouled spark plug story that could have been easily remedied by using the 'search' button". Please, I ask for your mercy as I explain myself :) I have searched and favorite'ed and re-read and seem to be stuck. But I have a feeling...

Hi, I'm Looking for some ideas on why this could be happening... Problem: It runs great until I go down a long steep hill and then the bike begins to hesitate, then backfires and eventually dies. It doesn't matter if I'm on or off the throttle. Every time I find both spark plugs are fouled. I...