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Hart0506

Fmf power bomb jetting?!?!

8 posts in this topic

I just purchased an fmf power pomp header with an fmf powercore 4 slip on... Installing on an 08 yz450f... What should I do to the carb to compliment the exhaust?

 

And also, ask yourself this question, "Does my bike run to my satisfaction?"

If it doesn't hesitate, bog down at certain RPMs, back fire, turn the exhaust blue or glow red, then leave it alone.

Some exhaust pipes just don't require the carbs to be re-jetted.

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The exhaust on the 08yz450f is a short one. They did it to save on weight, chokes up the bike in my opinion. The powercore is a few inches (by few I mean 5 or 6)longer then what the stock pipe is.. I've done some research and this model bike usually requires a jet change when switching to aftermarket exhaust. I haven't installed it yet so not sure how the bike responds, like you said I may not even need too... Exhaust is still in the mail.. Just wanted to see if anyone with the same year 450 has some light to shed on this topic

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The exhaust on the 08yz450f is a short one. They did it to save on weight, chokes up the bike in my opinion. The powercore is a few inches (by few I mean 5 or 6)longer then what the stock pipe is.. I've done some research and this model bike usually requires a jet change when switching to aftermarket exhaust. I haven't installed it yet so not sure how the bike responds, like you said I may not even need too... Exhaust is still in the mail.. Just wanted to see if anyone with the same year 450 has some light to shed on this topic

 

Well in that case, yes you'll likely need to re-jet it since they've modified the stock exhaust and you say it chokes the bike a bit. Your new set up will really open the bike up and let her breathe. I had an 06 YZ450F and switched to the same slip on but never ended up needing to re-jet luckily.

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Look through the jetting DB.  Plenty of info on '08-'09 models with aftermarket pipes.

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So, what was the verdict. Jetting ok? I have mega /4.1 combo on its way. I sprung for jetting kit to be prepared.

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Still haven't got the bike started yet. Got it all back together. Turned the gas on to the carb and it started leaking out of it through the swivel fitting so I gotta take care of that issue first. I'll keep ya posted. Sorry for the late response haven't been on this for quite some time.

Any luck with your new set up ?

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