# backfiring through intake



## countryboy61283

Anybody knows what cause this? Motor is brand new exhaust is stock but if u cruze around 10-15mph it will backfire threw the intake


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## BruteForceParts

I want in on this post. Mine does this too. It hasn’t bothered me enough to type up a post about it yet but I figured I would get in on this post and see what everyone else has to say. 

Mine does it especially when it isn’t warmed up all the way and more between 1mph and probably 8mph.


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## CTBruterider

Mine will do the same if I run 87 octane... When I run 91+ it just about eliminates all of my air box popping


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## 2domn8

usually to rich pops the exhaust and to lean threw the intake. Give me a shout if you need any help


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## BruteForceParts

So is that to suggest that it’s too lean and it “levels out” as the speed increases above 10mph? How would you approach fixing that without making it too rich at speeds above 10mph?

Does my question make sense? It *sort of* makes sense to me.


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## papaslim

*backfire*



countryboy61283 said:


> Anybody knows what cause this? Motor is brand new exhaust is stock but if u cruze around 10-15mph it will backfire threw the intake


use high octane even a lil race gas helps plus it smells good and it makes the guy/girl cry behind you cry lol


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## NMKawierider

Take your pick. Popping back through the intakes is caused by extreen leaning. With carbed machines, that can be because of a cracked carb boot...which is even possible with 08-09 injected engines, low fuel levels in the bowls from weak supply, partly blocked or worse slow circuts.. as in pilots, water in the bowles, CV slides not reacting as in sticky or split diaphram, way too small main jets if its happens in the 2400+rpm or additional air entering airbox. Popping can also be caused by a leaking intake valve...and it only takes one tiny leak.


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## 650Brute

BruteForceParts said:


> I want in on this post. Mine does this too. It hasn’t bothered me enough to type up a post about it yet but I figured I would get in on this post and see what everyone else has to say.
> 
> Mine does it especially when it isn’t warmed up all the way and more between 1mph and probably 8mph.


Same here, but after it warms up. Zero issues. We were thinking of a rejet, but honestly I think it's just the nature of these carb'd Brutes.

I have taken note of this for some time... And just seems to be before the machine is "warmed up"... We were messing with it in the shop, and initially, your like "wow, really need to richen it up....." of course those are all cold starts, and less than 10 min run time. Take it out, let it warm up, no popping thru the airbox, no sputter on acceleration.

You notice this also?


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## BruteForceParts

Exactly, once mine is warmed up it doesn’t do it anymore. What about you countryboy61283? Does your backfire through the intake only when it’s cold or does it do all the time?


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## 650Brute

I think it's just the nature of the beast, so to speak.


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## NMKawierider

650Brute said:


> I think it's just the nature of the beast, so to speak.


Well...realy it shouldn't especialy after warm-up. They are a cold-natured beast though....lol


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## wyo58

Countryboys is a 09 which is injected. He also has a different exhaust system which probably doing it to the stock fuel map. I would also like to know if it continues after warm up, so we can go from there.


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## 650Brute

nmkawierider said:


> Well...realy it shouldn't especialy after warm-up. They are a cold-natured beast though....lol


Yeah, exactly.... After warm up, flawless..


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## countryboy61283

It does in constant at low speeds warmed up or not but half throttle or more runs great, I can hear a slight sucking noise towards front of airbox close to throttle body boots so I sprayed some starting fluid around them to check for leaks and couldn't tell, its got me confused


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## rmax

on the infected brutes , on the head where the old fuel pump lines hooked to them for suction ,i think that kawie just put a cap on it you might need to check it out, back fireing through the intake could have blown one off, this would cause intake leak an lean condition


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## wyo58

Also check the tubes going to the ISC valve, which controls idle from the ECU. They are vacumme lines three of them I believe. If they leak not only are you a lean condition, also the ISC valve would not be operating properly.


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## eagleeye76

650Brute said:


> Same here, but after it warms up. Zero issues. We were thinking of a rejet, but honestly I think it's just the nature of these carb'd Brutes.
> 
> I have taken note of this for some time... And just seems to be before the machine is "warmed up"... We were messing with it in the shop, and initially, your like "wow, really need to richen it up....." of course those are all cold starts, and less than 10 min run time. Take it out, let it warm up, no popping thru the airbox, no sputter on acceleration.
> 
> You notice this also?


 This exactly what mine does once and a while.


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## countryboy61283

Why would it lean out all of the sudden, thought 2inch snorkel would make it a little rich? Exhaust us stock


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