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Jetting 101.

89K views 158 replies 113 participants last post by  qes 
#1 ·
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.





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#3 ·
Originally posted by chaos@Jul 15 2006, 10:09 PM
Is the TPS the thing the pen is on? (I think thats the idle) Or is the where the arrow is? Im confused!
[snapback]454970[/snapback]​
The TPS is what the arrow is pointing to. The pen is pointing towards the idle screw.

Good tutorial for the beginners. :clap:
 
#8 ·
Best to mark tps with a scratch to case, if it moves you will know.
 
#9 ·
I have an 06....I pulled out the needle to change the clip setting, but there is only 1 notch. I has NGN R stamped on it.
 
#11 ·
Originally posted by YFZ450alterego@Aug 15 2006, 02:19 PM
Most of the 06s' come with a non-adjustable needle........you would need to order a NCVQ needle froman 04 YZ450 dirt bike or a stock needle for the 04-05 YFZ to have any adjustments.
[snapback]470086[/snapback]​
Thanks! I just put in a 168main and 45 pilot....seems to be running ok. I adjusted the idle up and it seemed to get rid of the bogging. I was just frustrated when I finally got the needle out to see that I couldnt do anything with it.
 
#13 ·
ok, i hope someone can help me, i did a cam mod and rode it and evrything was great, them i removed the vaccum housing on the subframe and the it idled ok then i put it up and t wo days later, it sucks, mid range and upper throttle, nothing there falls on its face like its starving for gas or to fat. if i mess with the tps sensor or unplug and plug it back in or even bump it, will it do that and i f so can i fix it?
 
#15 ·
jdthomas24.....it may not be a jetting problem you're encountering. Is the battery fully charged? What year YFZ is it?

hotrodchev4x4...if I'm not mistaken the leak jet is mounted in the float bowl. I've never touched mine and luckily don't have the infamous bog that alot of people encounter. :icon_neutral:
 
#17 ·
ok uh...mine doesnt have the mixture screw knob. its just a hole. what do i do?
[/b]
:loser:



Do you remember posting that smiley in a reply somewhere...kinda sucks asking a legitimate question and someone's a smartass isn't it. Food for thought. :icon_biggrin:
 
#23 ·
Thanks for this how to rejet thread. Very helpful. Made the job alot easier. Great work!!!!

I have a new bone stock 2007 yfz450 (first yamaha quad) with a very fustrating bog off idle. Most threads I have seen acknoledge this and say to rejet and change to 4th clip position on the needle.

I could not rotate the carb enough to access it. Looks like its hitting something. I had to remove it from the engine. Not terrible but a little more involved. I also noticed that my 2007 needle is not adjustable. Only one clip position. I rejetted the pilot and main (now at 45/168) but I am stumped on the needle. Some say to shim it, I am not familiar with shimming. Will a 2006 needle work in a 2007? Any help? The bog lessoned with the rejetting but still stubbles when stabbing the throttle just off idle. My next step is to figure out how to shim the needle and add a power now unit.

I want to make this bog go away completley on my 2007. Does race gas help. I am using pumped gas at 93 octane.
 
#24 ·
I'm having that problem right now with my 06. I have a full HMF exhaust with 50 pilot and 175 main (had a 180 but changed it when the temp hit 105 everyday here in Dallas). Everything seems to be working right through all RPMs, the only problem I have is a stumble when stabbing the thottle right off of idle. I was thinking about adjusting the fuel mixture screw.
Anyone have any thoughts?
 
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