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i have an 07 yfz 450 with pipe, lid off, and a gytr needle, but its cold here in minnesota and it seems to be running lean, any ideas what i should run for about 30 degrees?
 

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Altitude 1300ft above sea level. I have a 06 478 bb. Ported head, web cams, ported carb ncqv needle 4th clip, main jet 180, pilot 50 ,running a fuel intake and hmf full exhaust. My quad acts/sounds like it's hitting the rev at full throttle in every gear when drag racing. I don't notice it when I roll into the throttle when trail riding.
 

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So i think i've gone through all 56 pages but am still coming up short with a set up for winter jetting. maybe i missed something. I have an 05 that i just bought, have no clue what jets are in it but i have everything ready to go to get it running right.

mods are:
Yoshimura exhaust (not sure if its slip on or full)
Fci
cam mod
zip tie mod

temps are -10c on average at about 400-800ft about sea level

anyone tell me what i should be putting in it?
 

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06 yfz 501 sparks pipe fci intake 150ft above sea level 75Fdegees 200m 45 p little poping and dies when i pull the choke out....what the hecks wrong
 

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I have 05 yfz 450 478bb +1.4 stroker crank and 178 main 48 pilot and i cant get it to run for nothing in the higher gears it cuts out and have to shut it off and restart it but if i block the back wheels up and go through the gears and even wrap out 5th gear it does just fine
 

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I have a ss/sb 06 with a fci and a sparks big core exhaust. I was wondering if the recommended jetting of a 45 pilot 175 main 4th clip nvcq needle would be good or if it should be different with the fci. I am at about 500ft elevation. Thanks in advance
 

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I've got a 2008 YFZ with a K&N filter, with pro design adapter. FMF exhaust with power bomb header, NVCQ needle, cam mod, and a CP 12:75:1 piston. I currently have a 180 main 45 pilot and I can't remember what settings I have for the air fuel or needle clip settings, it was running perfect before I installed the High Comp piston (plug colour etc. perfect, great power delivery) now it's popping like crazy and missing bad when it gets hotter ?! ADVICE PLEASE !! Thanks in advance!


(I'm in Ireland so no extreme temps and elevation is sea level)
 

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I put mine at the recommended 168m 45p and 1.5 turn out on af screw... Only thing done to mine is the baffle out stock exhaust and lid off.... And it's way to rich and I'm at 300 ft sea level.. So I'm going to have to go down on my main
 

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Just recently added full yoshimura rs2 system air box lid off and a uni filter...current setup is 168m....45p....1.5 turn out af screw and I still have that bog when I hit the gas...do I need to do the mysterious zip tie mod??? I'm at 500ft elevation
 

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Some please help! I have a 06 yfz 450 with FMF power bomb header and HMF exhaust pipe. Anyone recommend jetting numbers for this? I re jetted it but it baugs way down when I throttle it, then takes off properly. And it won't idle cold. Thanks!
 

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FCI no air box
Dasa classic shorty full exhaust
Cam mod
478cc bb
Vertex 12.1 compression

200ft elevation
110 gas

48 pilot 2.5 turns out
Ncvq 4th clip from top
188 main jet

Pulls hard but i dont know if i should drop main to a 185

Dasa says to use 185 main with only their exhaust and fci?? Help
 

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Are the stock jetting tips at the very beginning of this thread going to apply to a 2012 yfz 450?
I ask because the thread was started and those tips written in 2003...it's now just about 2016..13 years have passed..so do those jetting tips / guidelines still apply for my 2012 quad?
Thanks!!!
 

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Hey guys,

I'm at 1000-1300' in southwestern Ontario. I have the following done to the quad:
- mbrp exhaust
- uni filter no lid
- cam mod
I put a 170 main, 45 pilot jets in and an adjustable needle I got from eBay on the 4th clip. I'm not sure what brand the needle is, there's no markings on it. The bike is hesitating at mid-rangle throttle with some smoke coming out the pipe during hesitation. Any thoughts on changes?

Thanks!
 

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Probably be the 1000th person to ask this but i need a little advice on my jetting. Just really need a point to start at. I have Stage 3 hot cams, Barker full system in frame exhaust, no air box with K&N. I have all stock carb jets. I ordered a fuel mixture screw and not sure if i need to order a jet kit or order a YZ needle and individual jets. What do you guys think? I have been told to stay away from the DJ jet kit. I am at 2861 elevation.
 

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Probably be the 1000th person to ask this but i need a little advice on my jetting. Just really need a point to start at. I have Stage 3 hot cams, Barker full system in frame exhaust, no air box with K&N. I have all stock carb jets. I ordered a fuel mixture screw and not sure if i need to order a jet kit or order a YZ needle and individual jets. What do you guys think? I have been told to stay away from the DJ jet kit. I am at 2861 elevation.
Ok from what I have read on this thread I believe i need to start with...

170 main
45 pilot
50 leak jet
2.5 turns out
#5 slot on GYTR needle

Do you guys think that will get me in the ball park for my first test?
 

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Ok from what I have read on this thread I believe i need to start with...

170 main
45 pilot
50 leak jet
2.5 turns out
#5 slot on GYTR needle

Do you guys think that will get me in the ball park for my first test?[/QUOTE.]

should be a good starting point.
 

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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 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

my jd kit came with 165m and a 170m I'm in nj below 1500 ft and tops 95 degrees all summer. you suggest a 165 or a 170 with the blue needle 3 clip?
exhaust is power bomb with 4.1 , air box lid off, cam mod
 
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