06YZ450F Back Fires!

Picked up my bike today, got it home and it back fires, Pops, & spits coolant. Seems to be running lean. I called my dealer and they said to turn the air mixture screw but it's not helping.

I picked mine up tonight too, it backfired A LOT, but I only ran it for one minute and its 38 degrees here, don't know if that has something to do with it...will break it in this weekend and see if its still an issue.

Mine backfired a little but I let mine warm up and heat the exhaust packing and it seemed to be fine. you have 30 days if you think it is a manufacturing defect.

Picked up my bike today, got it home and it back fires, Pops, & spits coolant. Seems to be running lean. I called my dealer and they said to turn the air mixture screw but it's not helping.

The "spits coolant" will only happen the first time you warm it up.

The dealer overfills the radiator and the thermal expansion of the coolant blows off the "overfilled amount" out past the radiator cap and out the overflow hose. :applause:

No Drama. Just the laws of physics and coolant happy mechanic... :ride:

Due to the weather this time of year, most of your bikes will be running lean. I know mine starts to backfire more and more as it gets colder.

Picked up my bike today, got it home and it back fires, Pops, & spits coolant. Seems to be running lean. I called my dealer and they said to turn the air mixture screw but it's not helping.

Funny advice since these bikes don't have air screws. Don't ever listen to that dealer again for mechanical advice. What you DO have is a fuel screw. Turn it out to make things a bit richer at small throttle openings. If it's cold out then you may very well be lean and need to fiddle with the jetting.

Mine did the same. Called the dealer, they said bring it in. The service guy like yamaha pisses me off because they just lose money because they have to take the carb apart because it is running way too lean.

Turn the fuel screw out in 1/4 turn increments. Also, double check where it is set. As the other posters said, the cooler temps cause the lean condition

Stock setting is out 2 1/8 turns. I tried as much as 3 3/4 turns and still back fires bad. It is in the mid 70's here and near sea level.

Try posting this in the jetting forum...

"Backfiring" out the exhaust on decel is normal.

That got your attention? Now let me say that what I said is only partly true, but partly true anyway.

It is normally caused by either an air leak in the exhaust system, usually the midpipe clamp, or the header flange, or a lean idle mixture, or possibly, both. Even so, when the exhaust is airtight, and the idle mixture is set so that the bike runs otherwise perfectly, it may, and often will, still pop "some". Just don't fatten up the idle mix to the point that the bike runs bad just to get rid of the noise. It hurts nothing, and means nothing. (although sometimes it means you didn't turn the gas on, and your bike is going to quit soon!)

will-burr is right about the radiator overflow. The correct procedure is to fill to the top and let the system force out what it has to to have it completely filled when hot. It is also true that these bikes do not suffer standing at idle very well, and will boil over in just about one minute if no air crosses the radiators, or if the engine is not revved repeatedly at the very least.

BTW, you do realize that your exhaust will glow a very distinct red if idled very long, don't you? That's normal, too, so when you see it, avoid taking the flak; don't ask.

mine did teh same caled teh dealer they said bring it in the service guy like yamaha pisses me off b/c they just lose money b/c they have to take the carb apart b/c it running way to lean
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You are killing me! :applause:

thanks Gray! :applause:

Got it! Had to go out 4 1/2 turns (from closed position). Thing was blasting out two foot flames before. Now sounds like a champ!

Got it! Had to go out 4 1/2 turns (from closed position). Thing was blasting out two foot flames before. Now sounds like a champ!

4 1/2 is a bit far on the fuel screw, they have been known to fall out if they are to loose. I'd go one step richer on the pilot jet and screw the fuel screw back in a bit.

"

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:ride::p :p :lol:

thats good stuff there, i'll have to remember that one :applause:

If you need to go out past 3 turns or so, go up one size on the pilot jet and turn that screw back in some. At 4 turns it will vibrate out on you...

If you need to go out past 3 turns or so, go up one size on the pilot jet and turn that screw back in some. At 4 turns it will vibrate out on you...

at least on the 03-05 models.....

4.5 seems too much to me too

You are killing me! :applause:

Don't you just luv that Nuevo shorthand..........Grey!

a new language.............

you are too funny MAN! :ride:

Picked up my bike today, got it home and it back fires, Pops, & spits coolant. Seems to be running lean. I called my dealer and they said to turn the air mixture screw but it's not helping.

Are you sure you're turning the right one?

Four-strokes dont have air screws...they have fuel screws.

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