12 WR450 Fuel issue - wont start

At an enduro race a couple weekends ago I stalled and dropped the bike on a hill. It would not start, even after cooling off. 

I got towed out (damn that sucked) and tried to roll start it several times along the way. No go, the motor turned over fine, but just stuttered.

This led me to believe there is no fuel going into the engine.


Searching told me it may have been a faulty lean angle sensor. However, I got the bike to fire up a week after it happened. It ran okay in neutral, but when I put it in gear and started riding it would stutter, nearly die, come back to life, nearly die, etc.


So it looks like it could be two things - 


clogged fuel filter

Clogged injector


However, more searching showed that on FI mx bikes, a bad capacitor would cause the same issues. My battery has been taking a shit on me, would this have the same effect on a WR?

stock battery, dies very quickly under use or sitting.


or is it the backup capacitor from dropping the bike?


So, what do you think it is?


I have not been able to really work on the bike due to being at college and not having the necessary tools. I will be home shortly and would like some input.

Edited by Lumberjack450

Rather than grasp at straws, I think you need the full Yamaha shop manual

I think you need to electrically test some of the various systems

ex: lean angle sensor, where is it (manual) put an ohmmeter across it

Lean the bike over and see if the switch opens up (or closes depending on how designed)



Oh geez! I almost missed what you said.

A bad or marginal battery will wreak havoc with an FI system

Don't sell yourself short and try to charge a shitty battery either

A good 12V battery shows 12.2 - 12.8V at rest (not being charged)

They can run without a battery just like a YZ.

I think I have ruled out the lean sensor because it runs, just shitty.

I will start with the battery and attempt to replace the fuel filter first.

Any idea where the filter is located? I can't seem to find it on a parts schematic

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