05 wr 450 backfiring on deceleration?

[dmack]

Hey guys, whats up with this thing backfiring on deceleration?

I have done all of the "free mods"

gray wire

throttle stop

snorkle

Is this normal, or how can I fix it.

Thanks

[motojason]

Remove the AIS. That will help to get rid of the lean condition in the exhaust that is causing the backfire. TT store has a good plug kit for sealing up the holes once the parts are removed.

[dmack]

thanks moto jason

what does the ais actually do?

and does it rob power ?

[byggd]

AIS Air Injection System aka smog pump. Yamaha added it for 05 450 to get it green stickered.

[moach1]

does not rob power. once i removed mine, no more popping. i think the ais removal kit is a must have!!

[Fredneck75]

Removing the AIS alone may not be enough. You will probably want to rejet to get it just right.

[clark4131]

For an '05, backfiring on deceleration is usually caused by one or a combination of the following:

• AIS
  
• Lean needle position
  
• Lean fuel screw adjustment
  
• Lean pilot circuit
  
• Loose connections in the exhaust system
  

Check and adjust each of these individually and you'll figure it out...SC

[cgrlvr35]

Is that just for the California bikes purchased in that state? I bought mine in Oregon. Do you have a photo odf the AIS procedure?

[farkawi]

I'm at 5280' and mine still popped after AIS removal till I rejetted. I'm running a 50 pilot which is a bit rich (waiting for a 48) I raised the needle by inserting a .020" washer under the needle clip. You have to pop the aluminum plug outa the float bowl side to get access to the fuel screw which I'm running at 2-2 1/2 turns out.

[clutchinoregon]

what about the yz 450? ( 05 ) mine too has a little popping on decel. dealer told me normal... but id sure like to get rid of it

[Dan_Lorenze]

I'm not so sure I'd blame it on the AIS.. I would say there's a 90% chance your Pilot jet is too lean... All these "Free mods" will do very little without proper jetting specs... Go to the Jetting Database and see what we're all runnin... ?

[motojason]

Dan is right about it not being all related to the AIS. I meant do the AIS removal and then re-jet. I've got a JD kit and am using the settings recommended in the Jetting Database. Now my bike runs great!