Jetting FAQ's

[edgerat]

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 rougly 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 mixture
Stock YFZ with a much needed re-jet: 168 m 45p #4 clip 2 turns mciture
YFZ w/baffle out: same as above
YFZ w/baffle out and lid off: #5 or #6 clip same settings as above.
YFZ wpipe 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 for sure thing across the board but these are VERY close guidelines that you can use to get your YFZ450 to run like it should. I hope this helps get rid of some of the jetting posts that we see everyday. 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.
Thank you,
Isaac

[FAST1]

Isaac,
Would you also post the specs provided with the GYT-R jet kit
and the different combinations of pipe and intake for specific elevations.

I've not seen them myself, but have heard they also have recommendations
included with their jet kit and pipes.

[vorra65]

Isaac,

Good post bruddah! YDM (you da man) :rock

[edgerat]

I am not sure if you are asking what needle I was talking about in the first bunch of settings?? That is with the stock NCVR needle that comes in the carb stock.

The GYTR kit has a NCVQ needle in it. That needle is almost identical to JD"s red(leaner) needle. So, if you would look at it from the perspective that the GYTR needle is going to be about two clips leaner than the BLUE JD needle or 1 clip leaner than the RED needle. I hope this answers your question.

[YFZ-suprfly]

i have the GYTR kit installed exactly like you have stated..@sea level mine ya... BUT i dont have a pipe (yet :) ) but i do have the spark arrester out and the lid off... and i cant even describe how well it runs sounds and performs... i highly recomend doing this if you only got 50 bucks to spend right now... its worth it... good post btw!! :woo

[vorra65]

Great topic!

Just finished 1st rejet/mod


Elev. approx. 250 ft (Sacramento)
Bone stock
A/B lid on
Changed main to 165
Pilot to 45
5th notch on the needle
Pulled the baffle out, but felt like it took away on the bottom end-so put it back in.

Took it for a rip down the block and back, YEEHAAA
It appears to have a bit more pull off throttle, will get a better opinion on Sunday. Did not get the stumble off throttle, like some are stating. :D

Can't wait to get my HMF next week (waiting patiently-sorta) and the YZF needle I ordered is on b/o. :(

[wannayfz]

OK i am new and have no idea about jetting and how to jet.
What would i have a stock yfz jetted at in kansas city (no idea on sea level)
what would it be jetted at with the baffle removed and no lid
what about if i was to buy a hmf full system would the jet kit that comes with it be good enough?
Once again i have no clue on these things and would love to learn how to do all of my own work on my own bike
thanks

[vorra65]

Kansas City MO Elev. approx.- 750 ft.

>What would i have a stock yfz jetted at in kansas city (no idea on sea level)

refer to Isaac's post -

"These settings are for sea level if you are anywhere from 1500ft to sea level these settings should be very close to right on. "

Stock YFZ with a much needed re-jet: 168 m 45p #4 clip 2 turns mciture

>what would it be jetted at with the baffle removed and no lid<

YFZ w/baffle out and lid off: #5 or #6 clip same settings as above.

>what about if i was to buy a hmf full system would the jet kit that comes with it be good enough?<

I don't believe a jet kit "comes with". They reccomend you change the main to a 180. Which they sell for $5.

>Once again i have no clue on these things and would love to learn how to do all of my own work on my own bike<

Your'e gonna need some decent tools, and some basic mechanical knowledge. Buy a manual, either printed or on CD (ebay-$6-$7) and read read read---

[wannayfz]

Thank you vorra

[pahrump]

So if I am at 2000ft will I need bigger mains and pilot or smaller?

[edgerat]

PAH,
The further you go from Sea Level the leaner you get. Or the higher the elevation the smaller number on the jets.
Isaac

[YFZCentral]

How do you know if your bike is lean? Much like how the stock bike is, it felt fine to me. thx!

[pahrump]

Originally posted by edgerat@Sep 18 2003, 07:17 AM
PAH,
The further you go from Sea Level the leaner you get. Or the higher the elevation the smaller number on the jets.
Isaac

Thanks Issac that is what I have now learned.

So at 2000ft with baffle out lid off and cam mod a 168 main 45 pilot and 5-6 clip on stock needle?

What about with the YZ needle?

[edgerat]

MMMMMMMMMM, for that elevation I would say 165 main with 4 or 5 clip on stock needle and #2 or #3 clip on YZ needle depending on the heat. HIgher temps you need less fuel and low temps you need more gas.
Isaac

[pahrump]

Well thanks Edgerat!! :D

I finally made it to the shop to get a couple of jets, and got the baffle out, lid off, and cam mod,put the 168 main in, 45 pilot, moved the clip on the stock needle down to the 5th position. And all I can say is WOW :O its almost like I bought a whole new bike for the $8 bucks the jets cost me.


Anyone that has not done this yet I say DO IT!!

The POWER is great!!! :yfz

[pahrump]

By the way I am at 2000ft and it is 85-90 degrees here.

It might be a little rich but oh well it feels like lots of power everywhere, no stumbles or boggin at all!!!!

[EX 80]

The GYTR jet kit, does it come with the YZF450 needle or is it different. I am asking because i have many main jets and don't want to waste money by buying more.

[edgerat]

the GYTR kit comes with the NCVQ(OEM YZ450 needle) needle and two pilot jets.

[pahrump]

I have the dirtbike needle on order and it is only like 10-13 bucks.

So for 2 $4 jets and a $13 needle I have a redneck GYTR $50+ jet kit.

Cost me less than $22 total.

[450bret350]

anyone know the difference between the yz stock needle from the bike compared to dynojet needle