2005 WR450 won't idle without choke even when hot

G'day everyone,

 

I'm a long-time dirtbike fancier/new dirtbike owner of a 2005 WR450 which I purchased 2 months ago and have had the pleasure of giving a decent run a few times since getting it.  The bike seems reasonably solid (to a person who is very green with this sort of thing, but eager to learn) but there is an issue that is detracting from the fun and causing me, and some of my mates with bikes, some headaches as we can't work out why it's doing what it's doing.  The bike starts ok when cold with the choke on but will not run at all without the choke on unless I have some throttle.  If I have no throttle it will idle for 5-10 seconds then die.  When the bike is hot, I still need to have the choke on or as soon as I idle the same problem happens. I also have to have choke on to start it when it's hot.  My neighbour/mate who knows a lot more than me thought it may be a problem with jetting and pulled the carby off and cleaned it out, but everything looked fine and when put back together, the same thing was happening.  The bike hadn't been used very much over the past 2 years but had been serviced in the past 6 months before I got it (and not ridden since that service till I got it).

 

Apologies if its a stupid issue

 

Tim

That sounds like a typical pilot jet issue.  Pull it out and run a strand of wire through it and look at it with magnifying glass and bright light.  It doesn't take much of a film in a pilot jet to make it run lean in that range.  Better yet is to replace the pilot jet.  You may have to adjust the idle mixture adjustment screw to get it spot on, 2 turns out will put it close.

 Replace the pilot jet with new, if there is any green, white, or black corrosion. 

Then, using #15 fishing line, ream the passage above the pilot jet, getting past the sharp bend, and use lots of spray brake cleaner

Finally, treat your gas with ethanol treatment; every tank...

I ended up relenting and taking the bike to the mechanic after trying the suggestions above - turns out it was a very easy fix for him (and only cost $100) - there was a valve stuck in the float chamber so the fuel mixture was too rich cause it wasn't letting any air in.  I've spent a few hours on the bike since getting it back and it's running better than it ever was!!!!  Thanks for the help guys

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