WR450F won't run off choke...need advice

Hey everyone,

I'm working on a 2006 WR450F. The bike will run all day with the choke on but the second you push it in, the bike automatically dies. The bike was sitting for a while so I tore down the carb and cleaned it out. No change. So I pulled it down a second time, this time more thoroughly, and still no change.

The bike is completely stock with the exception of a cut grey wire and the baffle removed. Jetting is completely stock: 165 main, 45 pilot, 50 leak, and the needle only has one position. I fiddled with the fuel screw and at three turns out, it would idle for about two seconds before it would die.

I am completely stumped and starting to think that it's a jetting issue. Can anyone give me any advice. I want to make sure it is a possibility of lean jetting before I drop $80 on a JD jetting kit. Thanks for any info!

clean the carb out again . sounds like its running lean , something is plugged .

What altitude. My WR450 (2007) has the grey wire, throttle stop, air box restrictor removed, and a Q4. I had to jump to a 168 main. I can't remember what pilot jet I put in, but the leak is stock. I ride between sea level and 2000ft.

sounds like your pilot jet is plugged. Did you pull all your jets and hold them up to a light to look and see if they are clear?

I pulled all the jets, cleaned them and the passages twice and could see light through them. I'll try cleaning the pilot circuit one more time.

I'm running at sea level, 80-90 degree weather.

cracked, disloged rubber connecting carb to enging ?

leaking air making a lean situation ?

good luck


You have clogged passages in your carb. You have to clean it meticulously and thoroughly. Use carb cleaner, compressed air and be thorough.

It might be that you need to take it to a auto shop and have them heat clean it.

Be wary of carb cleaners and the FCR. You can ruin internal rubber parts.

I;d buy a new pilot jet and give it a whirl. sometimes, cleaning just does not work.

For sea level, you're running lean. Look at the Jetting Database in the Performance Index to get a ballpark idea of where you should be...SC

:eek: raise the idol?:p

Hot start plunger stuck in the open position?

I just had the exact same problem. I would spray carb cleaner in one end of a passage and it would come out the other end, I could see daylight through the jets as well. Clean right? Wrong. Try soaking it over night, there are areas in the pilot screw circut you just cant get to. Take out all the jets make sure you get the rubber O-ring out of the fuel mix screw, take the screen out of the float needle circut and any other plastic bits from the lower half. Don't remove the TPS. Only soak the bottom where all the passages are. Make sure it wont fall over and leave it overnight. I dipped mine in a solution of gas, fuel injector cleaner and carb cleaner. Blew it out w/ compressed air and viola. It took a while for the carb to prime but once it did all was good. It was able to warm up and run off choke so I could get it adjusted right. I think I read in one to the posts here that Yamaha makes a cleaner that you mix w/ gas that works well also. Good Luck Keep us posted.

Sorry I haven't replied, just started a new job. I have new jets on the way so once they come in, I'll clean the circuits again and let you all know. I appreciate the help.

sounds like mine yesterday. I had inadvertently messed with the idle screw. Turned the idle back up and then it ran just fine after popping the choke back in.

sounds like mine yesterday. I had inadvertently messed with the idle screw. Turned the idle back up and then it ran just fine after popping the choke back in.

There's something worth checking. Back to square one. My RM250 up and quit running one day. Dinked with it a little bit. No spark. Couldn't figure out for a week why it wouldn't spark. Finally noticed that the corner of the plastic kill switch button stuck.

Thanks everybody for all the help....it finally runs! Like everyone said, it was in the pilot circuit. I changed a combination of things at one time, installed the AIS removal kit, Zipty fuel screw, all the free mods, and rejetted. Now it runs great. The 48 pilot made the most difference but I think I still could go a size bigger.

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