WR450 instant power loss

Ive got a 2004 wr450 with a street title. Today i was riding home from work and i decided to take a little detour and hit some dirt roads up. I went around a turn shifted into third and when i opened her up it only got to about half throttle then the power just stopped. It was working perfectly fine up until that point. Now in any gear it idles perfectly, works good up until about half throttle and its like someone turns the off switch. It just bogs (thats the closest way to describe it) and wont go any faster.


It still starts first kick, idles goods, oil is new and good, coolant is good. It was getting dark when i got home so thats all i could check. What else should i look for to find this mysterious instant loss of power about half throttle?

Could an extremely dead battery cause this issue? Ive got a baja designs conversion kit on the bike and havnt ground floated my stator yet so im getting almost no dc power out of my stator and my battery is almost always near dead. It was more dead then usual today it just clicked when i tried to start it and i was running with my head light and taillight on.


If it was a clogged carb i wouldnt think it would be as instant as it was today thats why im thinking something electrical

It could be dozens of things.


What is your state of tune, last vavle adjustment, jetting, etc.

I agree,


check valves, jetting, dirty aircleaner/ carbs.. sp-plug etc..

Sounds like a blockage in the main jet.  The blockage could also be a puddle of water in the bottom of the bowl that gets sucked up into the jet past a certain rate of flow, shutting off the jet. 


Ironically, another thing that will cause very similar symptoms is if the main jet falls out.

Mine is an 05 with baja designs light kit. When my battery died it still ran fine, just had to kick start and no headlight if I remember correctly.  

Sorry for the delay in response i was out of town. The air filter is clean and looks like new. I bought it in september and i havent checked the valves and i do not know the history on the bike. It does however start first or second kick cold or hot so i was assuming the valves were good. I wouldnt think a valve issue would make a instant issue like this.


I bought a new battery on my way home from work tonight. First thing ill try is putting that in and see if anything changes. If not ill change the spark plug or look into carb issues. The way it happened i wouldnt think a plugged main. The main jet falling out is an interesting thought though. It could be water i will also try draining the carb and see if that fixes anything.


Ill report back when i know more tomorrow 



Turns out a dead battery was causing my issues. I put a new battery in and it worked perfectly. I put 50 miles on it today and all is well. Thanks for the suggestions everyone

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