250-500cc WR 250 running problem

Hi

I have problem with my 2005 WR250. I can't seem to get it running right.

I have messed around with carburetor and I can get it to rev pretty good when I adjust the air screw almost all the way closed but then it just barely idles for couple seconds after revving and even then it doesn't drop to idle just as fast as it should.
And if I open the air screw so that it idles good then it doesn't drop revs like it should. They just stay really high and race around for like 10 seconds and after that it drops to idle like it should.

Any ideas what could be the problem? I have tried the stock 430 and 400 main jets and 2nd and 3rd needle position. I'm not sure about pilot jet size. I have cleaned the carburetor all the way and made sure the jets are open.

If the throttle hangs after reving, your pilot jet is too lean try a larger size, the general rule of thumb is if the air screw is over two turns adjusted either direction the pilot needs changing.
Mains dont come into the range untill mid too half throttle.

good jetting info juicypips
if the bike has been sitting or if you don't run a fuel filter check for blockage in the pilot jet

Thanks guys, I checked the pilot jet, it seems to be size 35. It had little blockage and it got little better after cleaning it. Now I can get it to idle and rev without too much throttle hanging but it still takes couple second before idle settles. I also put in 400 main jet and needle on middle position. I guess I'll order size 40 pilot jet and see what happens.

dunno bout the 250s but the 300s hang a little regardless of jetting i found. guess crank inertia/being bigger bore. it aint no 85/125!

If a 40 pilot doesn't fix it then look for a small air leak around the intake and reeds. Spraying carb cleaner around the reed block should not change the idle... if it does you have an air leak. It's best to use Honda CR250 reed block paper gaskets on the Husky reed block. My 09 WR250 was perfect with a 37.5 pilot but I've since switched to a Lectron and it's way better and trouble free in weather and altitude changes.

Shawry lies his 3hunny is perfect no hang or anything just clean tree eating power.

its been eating pine trees all last week juicy. cut in a 3.3km track next to where we parked the ute & included every downed tree log/stump/termite mound i could find. kids & dog loved marking it out(plus counts as family time) . brutal to ride all 1-3 gear. if u dont like logs youd hate it. sorry for derail back to it people.

If it's the Mikuni carb- check the slide. Mine was wearing out and sucking air. I could never get it adjusted correctly.

I managed to brake the cable holder from carburetor. Have to wait couple days to get new one. But new odd problem has occurred. It tends to foul plugs now. I have put around 25 hours total on this bike now and I think I didn't change the plug for the first 15 hours.
Now I have burned through 5 plugs in 3 hours. Yesterday I rode for half and hour, it was fine, but when I tried to get going again today it started and died after couple seconds. Any idea why this is happening? Could it be plug cap?
Plug doesn't seem to have any particular color, maybe the tip is a bit black. And the jetting is the same as before so I don't think thats the reason now. I'm using br8eg plugs.

So I got the new cable holder and some jets. I'm now running with 40 pilot and 380 main. Bottom power got much better. Still doesn't drop revs straight trough but it is manageable. And plug lasted little longer, managed to ride about 2 hours with it. Now it seems like the tip is black so I guess I will lower the needle to 2nd clip. Hopefully this helps with the plug fouling...

Lost compression today... Thought it was another plug fouling but now I can move kickstarter with my hand. I guess I'll start ripping engine apart tomorrow. Hopefully cylinder is ok. And atleast after that I will know that the running problem doesn't come from the engine itself.