Jetting 101.

83680 Views 158 Replies 113 Participants Last post by qes, 17 d ago

Duane

Discussion Starter · Jul 7, 2006

How to jet the carb on the YFZ.

Step 1: Drain the carb of gas.

Step 2: Unplug the TPS and carb switches to spin the carb. Unplugging is optional. You may have enough room to rotate carb without removing the plugs.

Step 3: Loosen clamps that hold the carb. One on the intake side (not shown) and one on the leaving side of the carb.

Step 4: Spin carb to access the jets by removing the 17mm nut at the bottom of the carb bowl.

Step 5: Replace jets as required. In these pics I removed the bottom of the carb to get better pics. YOU DON'T NEED TO DO THIS!

Step 6: Getting to the needle and clip. Remove the plate on top of the carb.

Under the plate you'll find an allen head screw that needs to be removed to get to the needle and clip.

Remove allen head bolt to remove the needle and clip.

Reach inside the back of the carb to "lift" the needle out.

Needle and clip.

WARNING: DO NOT MOVE THE TPS SWITCH WHILE DOING THIS!

That's my basic "jetting for dummies" tutorial. Make sure everything is clean before doing any of this because dirt is your worst enemy. After you're done make sure everything is put back in place and all switches are plugged in.

EDIT: This is what you'll see on the 06-07 YFZ's when it comes to the fuel screw access. Thanks to Fever2ride for providing the pics.

Yamaha blocked off the access with a plug and you can either pop the plug out by screwing in a sheetmetal screw or take the bowl off and punch it out from the inside.

[attachment=4730:effects3.gif]

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17

141 - 159 of 159 Posts

crawlerman

· #141 · Mar 21, 2011

my 08se does not have but 1 place on the needle where the clip can go. WTH

jannypan

· #142 · Apr 9, 2011

Is the TPS the thing the pen is on? (I think thats the idle) Or is the where the arrow is? Im confused!

The Calamity

· #143 · Apr 10, 2011

Ive searched high and low for someone with same setup as me and close elevation and i cant seem to find info..

I got a new 08 yfz450 se about 4 months ago..
I put these mods on within a month ago

Mods are:
Sparks racing x-6 Full pipe (with SA screen installed)
Sparks filter with lid removed
Sparks Jet kit.
175 Main
45 Pilot
4th clip on needle from top
2 turns out

The throttle response is great.. from idle to WOT it screams.. with no backfires on deceleration.. my problem lies from 1/4 to 1/2 throttle. if i hold it between there is feels like it misses/sputters. I thought maybe i was rich in the main.. i tried a 170 and made it worse and also had backfires on the decel. Went back to 175. Not sure if i should try fuel/air screw or which way to go on the needle..

Anyone point me in the right direction?

Oh.. elevation is 2000 feet 60-90f normally

TY for your time,
Chris

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Sparty

· #144 · Apr 18, 2011

Could someone send me the photos also? Also where are you guys buying the jetting kits (jdjetting.com?)

cootertrucks

· #145 · Apr 22, 2011

The Example pictures are missing. help please???

07_YFZ450

· #146 · May 5, 2011

I live at 800ft above sea level....I bought an 07yfz from a guy about a week ago and cannot get the jetting right at all.....I just want to go back to stock does anyone know the stock sizes? I know looking at the bottom of the carb in a line the top is pilot, center is main, and bottom is ? if the leak is in the bowl? Anyone?

ninjayfz

· #147 · May 22, 2011

im having problems getting my jetting right. idle seems to be OK. i think it might be on he rich side. im not having any problems on the wot. but in mid range its not running right..i think it would be called 'hesitating'. it acts like its lean to me but when i move the clip to richen it gets worse. same as if i leaned it..

i dont know what else to do besides having a shop shop do it and spending $$$$.

1000 ft
big bore 480
ncvq 5th
boyesen quick shot
main 185
pilot 58
mixture 4 turns
sparks exhaust
k&n
air lid on

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yfz&f4i

· #148 · Jun 12, 2011

This sticky is worthless without the photos. Come on guys, any chance you can get those photos back up here and make this thread official again.

Brillo

· #149 · Sep 2, 2011

I have an 08 with a lrd pro4r and a k&n with the lid off. I run at 1600 ft in antigo wi and it has a 165 main, 45 pilot and it runs great except for after you keep it full throttle for a few seconds in 5th gear and it seems like the choke doesnt really do anything at idle. Am I runny too small of a main jet?

YFZ450~BENCE

· #150 · Sep 10, 2011

ya i dont know why people delete photos from their photobucket or delete the account. Ive had mine for years and just leave it alone, its just there just so it can be just there when i need it. haha

RichM1983

· #151 · Sep 18, 2011

I don't want to create a new thread for this so hopefully someone in here can help. The main jet is a 175, the leak jet is a 90, and the pilot doesn't have a number? I have no way of knowing what it is. Air screw is 2 turns out and the clip is a on the 3rd one down from the top. My mods are no sparky in exhaust and no lid. Otherwise stock.

My question: Should the jetting be ok?
What size pilot do I have since it has no number?

rodney-meeks

· #152 · Oct 31, 2011

Where can i go to see the pics to this awesome write up

yernkie

· #153 · Feb 18, 2012

Pics would be great. Can anyone forward them to my email ([email protected])?

alabaster

· #154 · Mar 18, 2012

ninjayfz said:
im having problems getting my jetting right. idle seems to be OK. i think it might be on he rich side. im not having any problems on the wot. but in mid range its not running right..i think it would be called 'hesitating'. it acts like its lean to me but when i move the clip to richen it gets worse. same as if i leaned it..

i dont know what else to do besides having a shop shop do it and spending $$$$.

1000 ft
big bore 480
ncvq 5th
boyesen quick shot
main 185
pilot 58
mixture 4 turns
sparks exhaust
k&n
air lid on

ninja did you ever take yours to the shop?

i have the same issue. i just added:

hmf performance exhaust system
gytr jets:
170 main
48 pilot
3 turns on the pilot
ncvq 4th (was on 6th)
stock air filter w/ lid off (i've rode down the street with no filter on as well)

I am about 2000 ft above sea level in Las Vegas. At one point i was shooting lots of flames out the pipe after just the exhaust and jetting. then i added the needle and from 0-25% throttle it rips, 25-50% is $h!t and 50-100% rips. I've messed with the needle and it doesnt seem to help.

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tihs

· #155 · Aug 15, 2012

just getting mine dialed in - around 500Feet
FMF Slip on
96mm Bore.
06+ crank
open air box
cam mod
K/n filter

Pilot 42
152 Main Jet ( a tad bit rich ) going to drop to a 150 or 148
i think it is a DynoJet needle - not sure what spot but it is a bit rich going to drop it 1.

I am using an O2 sensor to tune and I shoot for 13.2

idle is at 13.2 range
Mid is at 11.3 range
top is at 12.0 range

2004 YFZ

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LUGO

· #156 · Sep 12, 2012

Need the pictures for this thread or its worthless

just

· #157 · Oct 13, 2012

I have a 06. Yfz with;
K&N pro flow air filter with no lid.
ported head
stage 3 hot cams
high comp. piston
dynatec electronic
Akrapovič exhaust

Before I put a stage 3 cams was runing on 170 main jet, 45 pilot, 4 clip on niddle, and 1000ft above sea level ... Now i have a problem that engine is misfiring at mid throttle (spark plug is black)!

Wich jet settings should I use??:|

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Detroiter

· #158 · Apr 22, 2013

Yeah can OP or someone eles repost those pictures? This is about the only place/thread with detailed pics and i cant even see them ne more

qes

· #159 · 17 d ago

Detroiter said:
Yeah can OP or someone eles repost those pictures?

I happen to have the pics from the OP.. though I might be missing a couple at the end regarding the plug blocking access to the fuel screw

Duane said:
Step 1: Drain the carb of gas.

Step 2: Unplug the TPS and carb switches to spin the carb. Unplugging is optional. You may have enough room to rotate carb without removing the plugs.

Step 3: Loosen clamps that hold the carb. One on the intake side (not shown) and one on the leaving side of the carb.

Step 4: Spin carb to access the jets by removing the 17mm nut at the bottom of the carb bowl.

Step 5: Replace jets as required. In these pics I removed the bottom of the carb to get better pics. YOU DON'T NEED TO DO THIS!

Step 6: Getting to the needle and clip. Remove the plate on top of the carb.

Under the plate you'll find an allen head screw that needs to be removed to get to the needle and clip.

Remove allen head bolt to remove the needle and clip.

Reach inside the back of the carb to "lift" the needle out.

Needle and clip.

WARNING: DO NOT MOVE THE TPS SWITCH WHILE DOING THIS!

That's my basic "jetting for dummies" tutorial. Make sure everything is clean before doing any of this because dirt is your worst enemy. After you're done make sure everything is put back in place and all switches are plugged in.

EDIT: This is what you'll see on the 06-07 YFZ's when it comes to the fuel screw access. Thanks to Fever2ride for providing the pics.

Yamaha blocked off the access with a plug and you can either pop the plug out by screwing in a sheetmetal screw or take the bowl off and punch it out from the inside.

141 - 159 of 159 Posts