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need advice
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Posted by: wilsta

My friend just bought a o4 yfz450 and it not running quit right. it popping and back firing out the pipe and has poor throttle response. i pulled the carb off to clean it, it was fairly clean.

could the jetting be off or the valves be out of adjustment?

It has a stock air filter with out the lid
pro circuit t-4 silencer
main jet is 180
pilot jet is 42
jet needle is set to the 4th slot
I don't know if the other jet matter but they are
starter jet 90
pilot air jet 100
accelerator jet 50

Posted by: Xater

main jet sounds to big for just a slip on. try putting a 168 or 170 in it.