04 YZ 450 shutting off over jumps, occasionally?

First off, THANKS in advance! It's been almost a year since I've needed to post any questions here. Thats a good thing though, my 450 has performed flawless. Now however, it has just started to shut-off over the occsional jump. Not every time just once or twice during the day of riding about 4 or 5 20 minute sessions. But...when it does decide to do this, well lets just say I've dropped a few "F" bombs as I kissed the front fender. I think it's happening on some of the steeper jump faces, where you'd chop the throttle to bring the front end down? Also it's blubbering when the throttle is cracked open quickly. My thought is it might be the airscrew. It also has been "lean popping" during deceleration. The bike is stone stock. I'm a little intimidated by the 4 stroke (first ever 4 sroke) I've not messed with anything, including jetting. I'll probably try and get a new exhaust before our next MX season fires up here in September. As far as pipes, I'm considering FMF cause I can get a deal on one, DR D or TA. Any thoughts? Thanks Again! :thumbsup:

You say it blubbers when you crack the throttle quickly. I'd check the accellerator squirt. Fuel should be injected as the slide clears the intake. There is a procedure for adjustment in your owners manual.

As for the shut off i'd try process of elimination. disconnect the kill switch for a day and ride. Swap out a carb with a friend (gotta be a good friend) and test that for a day. Put the bike up on a stand (unweight the frame) start er up and shake it up. sounds like a nasty and scary problem so limit the air time till you figure it out.

Good luck.

It ran fine before, unless your weather or altitude has changed then there should be no need to make any jetting changes. Personally I would start by giving the carb a good cleaning. Shoot cleaner through every hole, followed by compressed air if you have any. Be sure to hit the two holes on the airbox side of the carb. If the pilot circuit gets goo in it then that can make these things run really badly at small throttle openings.

Yea a clean carb is a happy carb... because there really is no filter between your tank and the carb you can get dirt in there. Even an improperly oiled filter will let junk through and give you trouble... It is an intake out take thing, fallow sirthumpalot's advice and clean the carb, carful on the slide there is a small rubber seal that will expand when you get carb cleaner on it and will restrict the slide yadda yadda a long story short. if the carb is clean, check your plug, and your pipe, make sure your pipe's not loosing its packing and blocking anything... :thumbsup:

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