I have been working on my 2005 WR450 way longer into the riding season than I would like to.   I have a problem with the bike running without the choke on.   I have totally rebuilt the top end, to include valve adjustment and new rings.  The bike will just not run without the choke on.  I have fiddle-farted with the Air/Fuel and Idle adjustments so much I fear that I will wear out the threads!!   When I do ride the bike with the full choke on, it has extremely choppy throttle response.  I turn off the choke and it cuts out.  It appears the vacuum lines are correct.  It starts, so I know I have spark.  I have cleaned the carb so many times I feel like I am the Bo and Luke Duke of the 450 world.  There has go to be an answer, but I'm at a loss.  

Ream the passage above the pilot jet with real carb cleaner and light wire or fishing line

There is a tight bend in there that gathers corrosion and debris


Also, service the hot start plunger and cavity for corrosion/leaks


When you say you 'cleaned' the carb, unless you also replace the worn out areas, cleanliness won't help much

Krannie is probably right, it's a carb issue, but also check the exhaust and make sure you don't have any sort of restrictions, take the tip out and see if you notice any difference. 

If you have the stock WR exahust tip, it will never, ever run correctly.

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