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Fuel Pump thumping 12 wr450F...HELP PLS!!

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Hi All,


Long time reader, i've learned to fix my carb bikes over the past because of many contributors on TT however I need advice on this one as I am electrically retarded for want of a better word.


Bike will not start/ kick or button.

My 2012 WR450f will not prime when I press the on/off switch, rather I get 3 symptoms:

  1. On/off switch blinks constantly (not engine light)
  2. there is an audible constant thud,thud,thud coming from in-tank fuel pump
  3. Headlight, taillight are dim and blinking indicating low voltage. My speedo/timer screen is perfectly normal?

Things i've tried:

  • Changed battery/put on tender with same result as above
  • Taken fuel pump out of tank and tested briefly as not to run it while dry too long, whirls strong.
  • checked fuel filter while pump out, tried to clean as best as possible but could not take out of pump cage.
  • Off advice of another, tried to add extra ground wire from starter relay to bike frame.
  • Changed the starter relay to new OEM one.

I would really appreciate some advice on this one, ive looked it up on TT and the web but haven't found much similar, we do not have much help in terms of motorbike part shops and qualified bike mechanics here. Thanks in advance.




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You need a new pump.

The pump has been damaged from trying to run with a dirty filter (starvation). The filter can come out, and be replaced. You just have to be careful prying open the cage. Lot's of filters listed in goole search. https://www.google.com/search?q=yamaha+wr450f+fuel+pump+filter&oq=yamaha+wr450f+fuel+pump+filter&gs_l=psy-ab.3...1093.1709.0.2147.

You should be filtering you gas before putting it in the tank, AND treating the gas for contaminates like Ethanol, every tank.

The fuel is the only lubricant to the pump. You must not run it at all, dry.

If you don't trust my assesement, find out for your self using water and a PSI guage, which you can rent from any autoparts store.

You need to run it for 5 min at least, if it even can put out 60 psi...

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Thanks for the reply Krannie, that is the first real assessment I feel i've gotten, that makes sense.:thumbsup:

I Just want to know if a pump issue such that you have described is the cause of the voltage drop I am experiencing?

besides the pump, could there be anything else? if not then great I have direction

Yes I will start filtering/treating my gas from now on, I do not wish to push wr450 10km through jungle again.

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