2008 yz450f bogs when throttle opens

I had put on an FMF powerbomb exhaust system and changed the main jet from a 160 to a 170, and changed the needle from groove 3 to groove 4. Could this be the problem why when i give my bike a quick twist of the throttle it bogs? Im thinking its too rich. Any ideas?

You increased the flow of the motor, and now the accelerator pump can't keep up.


Change the a pump linkage spring to a Merge racing version, adjust the pump spray timing with the linkage screw, make sure you have a 50 leak jet, and it will be fine.

As per Krannie it needs more fuel when you give it a quick twist.


Might only need the leak jet smaller to sort out.

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