phazer air box

4

480 phazer

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Nov 14, 2009
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6
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53
Location
Racine,MN
86 phazer aaen pipe 150 mains. sled runs awsome with no airbox.put airbox on and will not rev past 5200 and just bogs.take box off again and runs mint.did this 3 times with same result. i dont have a clue. i need help.
 
DO NOT run it with out an air box!!! They are lean in the midrange to begin with. Is the motor stock? Have you gone through the clutches latley, ie good springs, tight rollers etc???
 
Why would you not run it without the airbox? I bumped up the main jet size to compensate. That needs to be changed whenever you pull off an airbox.

It's not like it's even an air filter
 
It would be fine on the mains if you ran wide open all the time. Most people use the midrange circut more than the mains, and the midrange on those is very lean to begin with and not very adjustable. to run w/o an airbox on a phazer, you need flatslides or roundslides not butterfly carbs, been there tried it, doesn't work with the butterflies!
 
is thare a mouse nest in the airbox. did you do the update to the stock carbs for mid range lean and performance pipe. its 40*F here today and all my sleds are a little doggy. you should run a airbox, maby you can take the guts out of it and duct some cold air into it....the airbox does help keep out belt dust, snow and maby a fire from a backfire... :dunno:
 
alot of airboxs are actually designed the flow better than no airbox at all.... sounds crazy but the airbox actually keeps the air velocity up and therefore flows better... now im not honestly sure if this hold true fopr the phaser airbox but i bet it does.... and it is ALWAYS safer, and better to run an airbox...
 
motor is stock besides the pipe.i took the box apart and cut some of the center section out and it runs perfect now. how do i fix the lean mid range that i keep reading about? thanks again
 
im not a real phaser guy but i dont think you can fix it with the stock carb... there are not enough circuts in that butterfly carb to fix the midrange without screwing something else.... i think thats why some guys switch to slide carbs
 
tyler440 said:
alot of airboxs are actually designed the flow better than no airbox at all.... sounds crazy but the airbox actually keeps the air velocity up and therefore flows better... now im not honestly sure if this hold true fopr the phaser airbox but i bet it does.... and it is ALWAYS safer, and better to run an airbox...
Click to expand...

Now there is a guy who knows his airboxes. Other then a ram air system which is the best, the airbox on many sled creates what is known as a "still air box". It will actually perform better then not running an airbox at all. Adding a Cold air kit (Bender Racing had a great kit) really does help. Both channeled cold air from the hood opening to the fan shroud, and an Airbox kit that was designed by Tim Bender himself.

On your carb tuning, like many seasoned 485 fan cooled motor guys will tell you, it's the midrange that really really really needs a strong fuel delivery from your carbs. See the link in this thread on the Yamaha factory Phazer carb update. Yes, it works. Be sure to look at the nozzle head (the one that protrudes into the carb venturi) and align both holes in the nozzle to how the instructions shown it. Very important. I have the following sled and run 145 mains with a dynojet kit.
 
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