Slip on exhaust YZ450f. Do I need to re-jet?

6 replies to this topic
  • mdenhaan

Posted January 10, 2010 - 09:49 PM


Hi guys,

I'm new on Thumper Talk. Just bought a mint condition YZ450f 06 was thinking about a slip on exhaust. If I get one, do I need to re-jet the bike? I keep hearing about having to re-jet when you get a pipe, but didn't know if that referred to an entire new exhaust system or if it applied even if you only did the slip on exhaust. Also any feedback on the procircuit 496? Got one cheap and haven't installed it yet.

Thanks for the help!

Big Mike

  • JDAM450

Posted January 10, 2010 - 10:46 PM


From what I understand you may need to rejet with a full exhaust system or new header. I installed my FMF Power Core 4 and did not need to rejet. I would give the 496 pipe a try.

  • grayracer513

Posted January 10, 2010 - 11:22 PM


It depends on the particular exhaust system you choose. Some yes, some no. Some richer, some leaner.

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  • motojase316

Posted January 11, 2010 - 01:05 AM


It depends on the particular exhaust system you choose. Some yes, some no. Some richer, some leaner.

Precisely, most exhaust manufactures will provide jetting info if it is required for their specific pipe, or their web sites will have jetting info for the system. last 3 fmf 4.1 systems I have bought states, "designed to run with stock jetting"

  • mdenhaan

Posted January 11, 2010 - 06:29 AM


Thanks for the feedback. I will check with Pro-circuit and see what they say.

  • joker34

Posted January 17, 2010 - 02:21 PM


yes you most likely will need to rejet

  • tek_01

Posted January 17, 2010 - 02:33 PM


I put a full jardine exhaust system on my 05 and i think it is running fine without rejetting
Starts 1-2nd kick cold and first kick warm (maybe more if in gear)
Has a very nice steady idle and does not backfire or pop normally unless its a real long deceleration with the revs up high.
Im no expert but i dont think i need to change anything, unless someone can convince me otherwise

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