2008 yamaha apex MTX backfiring at 7000 rpm and won't rev out

Push T Nytro

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Have a 2008 yamaha apex MTX, sled starts to backfire around 7000 rpm and will not rev up past 7000rpm. I hope someone can tell me what's wrong, thanks!
 

bigfish

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Does it have a turbo?

he posted this in the turbo section to its a mcx apex,it sounds like a boost leak to me,about where the mcx starts making boost,easy place to start is check your intercooler boots make sure they are all still sealed or change fuel filter if its never been done.
 

NM

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he posted this in the turbo section to its a mcx apex,it sounds like a boost leak to me,about where the mcx starts making boost,easy place to start is check your intercooler boots make sure they are all still sealed or change fuel filter if its never been done.
It would have to be a pretty bad boost leak to prevent it from going past 7000 rpm. Sounds to me like the extra injectors are not turning on and it's lean popping. Won't build boost or rpm without fuel.
 

Pistonbroke

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It would have to be a pretty bad boost leak to prevent it from going past 7000 rpm. Sounds to me like the extra injectors are not turning on and it's lean popping. Won't build boost or rpm without fuel.

If an intake boot or charge tube was right off, you would also hear a hell of an air whoosh and whistle that wasn't there before. Had it happen once and it's pretty obvious, and the sled won't pull hardly any rpm.
 

togo ripper

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Was helping with this sled and they have put a new mcx controller on all boots are tight and it looks like all the vacuum lines are on and tight, the secondary injectors do turn on she we apply 5psi at idle with air pump and it floods and kills the motor, the kit was on another sled that ran perfect in the spring they just switched to a lower mileage and year newer machine
 
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