Backfire issue

I have an 03 yamaha yz450f. It runs mint but every time i get on it then shut the gas i get a lot of little pops. How do i go about getting rid of my backfire

That's a lean popping from the pilot circuit. If it has just suddenly started doing this and you've made no adjustments, chances are the fuel screw and it's passage need cleaning. Check the condition of its oring too.

 

Otherwise, turn the fuel screw out 1/4 turn(richer) and  re evaluate.

Ive a fuel injected KTM and have just experienced the same problem. In this case how to alter the fuel injection system to stop the popping ?

Ive a fuel injected KTM and have just experienced the same problem. In this case how to alter the fuel injection system to stop the popping ?

 

A lean closed throttle condition is causing the problem.

 

If the problem has always been there, it's a lean map issue,

You don't state the year or model, so..........

 

If it's a new problem, you have an air leak........exhaust, TB boots, sensor ports, etc. 

 

If you also have rough running, you have dirty injectors.........but that usually never causes a lean condition.......

Hi Krannie,

It could be a small leak appearing between the silencer and mid pipe, but i heard theses models come lean out of the factory so i'll investigate both the exhaust and the TPS.

 

KTM 450 15.5 Factory Edition

 

26 hours running time

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