Our very own "edge" has compiled this great little jetting guide for all of you who are having problems, or need a starting point before you attempt to re-jet your YFZ450's FCR carburettor. Thanks, great! :tup:
This is a pretty basic outline for jetting on the YFZ450. These settings are for sea level if you are anywhere from 1500ft to sea level these settings should be very close to right on. Anything above 1500ft should lean the settings accordingly. Also, as a good adjustment, you should raise the idle by roughly 10 steps on the knob. The dealers set the idle way too low and that is a big cause for stalling these things.
Stock YFZ off the showroom floor: 158 main 42 pilot #3 clip on needle 2 turns the mixture
Stock YFZ with a much-needed re-jet: 168 m 45p #4 clip 2 turns mature
YFZ w/baffle out same as above
YFZ w/baffle out and lid off: #5 or #6 clip same settings as above.
YFZ wipe and lid on 168m 45p #5 or #6 clip should be very close
Now, for this next set of jetting, you will need to buy either a James Dean jet kit(www.jdjetting.com) or a GYTR jetting kit from your local dealer.
YFZ w/pipe and lid off GYTR needle #4 clip 168m 45p 2.5 turns mixture screw.
YFZ w/pipe and lid off JD blue needle #3 168m 45p 2.5 turns mixture screw.
The above settings are somewhat rich but this engine craves tons of fuel and tons of air to make big HP. I have yet to foul a plug running the JD Jetting settings on my YFZ with a Sparks pipe and the YZ exhaust cam. Also, all the pipes out for the YFZ are going to be pretty close to the same jetting-wise so this FAQ should get you pretty close. Again, these settings cannot be a sure thing across the board but these are VERY close guidelines that you can use to get your YFZ450 to run as it should. I hope this helps get rid of some of the jetting posts that we see every day. If you have any questions about how to alter your jetting to dial it in exactly please ask the questions here so that we can all learn from your testing.
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This is a pretty basic outline for jetting on the YFZ450. These settings are for sea level if you are anywhere from 1500ft to sea level these settings should be very close to right on. Anything above 1500ft should lean the settings accordingly. Also, as a good adjustment, you should raise the idle by roughly 10 steps on the knob. The dealers set the idle way too low and that is a big cause for stalling these things.
Stock YFZ off the showroom floor: 158 main 42 pilot #3 clip on needle 2 turns the mixture
Stock YFZ with a much-needed re-jet: 168 m 45p #4 clip 2 turns mature
YFZ w/baffle out same as above
YFZ w/baffle out and lid off: #5 or #6 clip same settings as above.
YFZ wipe and lid on 168m 45p #5 or #6 clip should be very close
Now, for this next set of jetting, you will need to buy either a James Dean jet kit(www.jdjetting.com) or a GYTR jetting kit from your local dealer.
YFZ w/pipe and lid off GYTR needle #4 clip 168m 45p 2.5 turns mixture screw.
YFZ w/pipe and lid off JD blue needle #3 168m 45p 2.5 turns mixture screw.
The above settings are somewhat rich but this engine craves tons of fuel and tons of air to make big HP. I have yet to foul a plug running the JD Jetting settings on my YFZ with a Sparks pipe and the YZ exhaust cam. Also, all the pipes out for the YFZ are going to be pretty close to the same jetting-wise so this FAQ should get you pretty close. Again, these settings cannot be a sure thing across the board but these are VERY close guidelines that you can use to get your YFZ450 to run as it should. I hope this helps get rid of some of the jetting posts that we see every day. If you have any questions about how to alter your jetting to dial it in exactly please ask the questions here so that we can all learn from your testing.
