A little history: A local racer buddy threw the rod on his old KX500 literally minutes before his race and since I had just finished my race I let him borrow my bike. The problem was that I didn't have any more fuel for my bike so borrowed fuel from another guy. He was an old school guy that liked to run a little bean oil in his gas...in the hurry to get my buddy to the start line on time I didn't think anything about it. My buddy was having a tough time with my bike flaming out during the race and I figured it was just the funky gas. Got home, dumped the funky gas and refilled with fresh gas. On Saturday when I first fired up my bike it ran for a bit, coughed and died. Took quite a few kicks to get it running again but it was running like s**t for a few minutes then cleaned up and ran perfectly. I figured I burned up whatever funky gas was left in the fuel line and didn't think any more about it. Fast forward about an hour into my race...everything has been running perfectly when all of a sudden it would bog like it was going to die when I hit wide open throttle. Back it off a bit and it runs perfect and strong. Low, mid, and high RPM all good...just can't go WOT without a wicked bad bog. Thinking there might be some contamination somewhere in the fuel system but I really don't know where/how to look for it. I disconnected the fuel line from the fuel pump to remove the tank and no fuel came out...is this an indication that there is a blockage in the fuel pump or is it normal for fuel not to come out when the bike is not running? How do I check and clean the fuel pump? Can the injector be cleaned? Any other thoughts?