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R top end Jetting

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My bike (07 450x) is apart for installing a 07 450R head and maintenance.

Before i put it back together i'd like to know if i should go any size up on jets or needle.

The jetting i've been running without the r top end was:

170 main

48 pilot

50 leak

ncvs #4

The mods:

Twinair / no backfire

airbox top cut

q4 can



Any suggestions on changing my jets before i put my carb back together?

If so what sizes?

p.s. I'm at sea level from 60 to 95 F.


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NJYR 3rd

Slow Jet 42

Main Jet 178

AS -1.75

Book does not list leak jet and I can't remember what it is off hand. It changed from '05 as I recall.

These are the factory carb specs for an '07 450R and they are near perfect at sea level. I've only had to adjust the air screw during extreme temperature and humidity changes.

Found a great thread on the R forum:


Edited by cubera

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