2013 Bad Bog at WOT

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?

Sounds like a fuel filter limiting the flow to where it can't keep up with the engine at WOT.  The pump will have to come out of the tank and get the screen cleaned out.  The problem is that no one (who knows why?) thought that the filter would ever need to be serviced, so no provision was ever made for it to be done as a simple service procedure.  

 

But someone here has boldly gone where I haven't:  http://www.thumpertalk.com/topic/1017998-2010-yz450-bogs-after-15-minutes/#entry10702600

 

Careful whose fuel you borrow :smirk:

Gray, thanks for the reply and the link (that I should have found myself with a proper search).

 

I was able to get the filter out without cutting the fuel line on the pump and found some serious gunk in there...not exactly sure what it is/was. If I had to guess I'd say it was some type of paper ore even remnants of an old low quality sticker.

 

I have it all back together but have not fired it up yet but I'm sure it's going to be good...certainly has to be an improvement after getting all that out of there.

IMG_6321.JPG

Sure would be nice if these bikes were made so that the pump was not in the tank and you had a separate upstream filter.

Believe it or not, that would complicate things.

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