04 YZ 450 shutting off over jumps, occasionally?

3 replies to this topic
  • blueblood221

Posted July 27, 2004 - 11:29 AM


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:

  • TexasDirtNap

Posted July 27, 2004 - 03:56 PM


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.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • sirthumpalot

Posted July 28, 2004 - 01:54 AM


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.

  • Hank

Posted July 28, 2004 - 07:05 AM


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:

Related Content


yz400f throttle bog by yz400fmaniac

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • * * * * *
  • Hot  28 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies

Need help by Goforaride

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  68 replies

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.