carb adjustment help needed

I have a 2003 yz450f which i have just put in a new piston and rings and new valve seals. I also raised the needle one position to take care of the popping on deceleration. Now when i start my bike i have to hold in the hotstart lever for it to soon as i let go of it..the bike shuts off...any suggestions would be greatly appreciated....thanks

Lower the needle one clip and adjust the fuel screw instead (richer = OUT). If you need more than 2.5 turns out (total) on the FS, put in a larger pilot jet.

Did you by chance remove the carb slide and reinstall it upside down?

thanks i'll try u know how much to turn the air screw out as well to get the settings just right on it?

You have to do it by "feel" really. Usually decel popping can be fixed with about 1/2 turn or so out. Depends on how bad it's popping.

So, figure out your current FS setting by counting the number of turns IN until it is lightly seated. Then return it to where it was.

Next, put the needle back to the position you had.

Now ride the bike and get it good and warm. Bring it back in and turn the FS out about 1/4 turn at a time until the decel popping "just" goes away while riding. I actually prefer my bike to have just a small amount of popping here and there - that's where I think you get the snappiest response. If you have to go more than 2.5 turns total, put in the next larger pilot jet.

thnx for ur help skthom2320 the plate on the carb slide was upside down...runs great now :)

No problem, as long as you don't ask skthom2320 how he knew that could be the problem. :)

No problem, as long as you don't ask skthom2320 how he knew that could be the problem. :p


Im having trouble getting my bike to run good so I have been reading all posts about carb settings. I was wondering what the plate on the carb slide is and how I can tell if it is upside down or right side up? Thanks.

The flat part of the plate is on the bottom it's a common mistake They should put an arrow on it! This side up

When you say plate do you mean the plate that you see when looking in side the intake port?

no...the plate is on the motor side of the carb....when u take the top cover off the carb u should see a gold phillips screw and an allen screw....if u remove the phillips screw and take out the slide the plate is on the motor careful because it will fall off if u dont have a hold of it...and if it's on upside down it won't allow enough air into the motor....just remember the flat side of the plate goes down.....

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