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Jetting 101.

83680 Views 158 Replies 113 Participants Last post by  qes
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.


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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my hat in the ring for pics as well. Thanks!

[email protected]
Wow nice post sort of long tho, hahahaha im new here and practically new to my YFZ too, i started with the famous Blaster :D.... well getting back, great post... im having a few backfires after releasing my throttle so ill try to buy a differente needle cuz the one i have only has 1 position or well buy a different Pilot jet
Can you send me the picture to [email protected] I would greatly appeciate it thanks.
elevation question

hey guys i live at about 2500 ft and im jetting my 04 yfz for glamis i have read that people use a 175 main and a 45-48 pilot i have a 45 in mine with the a/f turned out 2. im am getting alot of popping after i let off the gas is this normal? what is the saying like elevation wise lean at higher elevation and richer at low? any advice would be appreciated and my mods are in my sig
Could I get you to end me the pics and info to [email protected]
the easiest way i have found to get needle out was use a pair of tweezers they help amazing especially if you have big fingers!!!!!!!
Do u have to jet it when u get a new exausted and do u do this with fuel injection?
Jetting a High Mod 06

Just dropped in a +3 crank (471 cc ) a pair of stage 3 hot cams and 12 to 1 Wisco piston.
Have a Trinity stage 4 exhaust and head is port and polished.
Any advice on jetting for 5000 ft elevation??:clap
Hi Guys
sorry to do this but can anyone out there please help.i fitted a scorpion full system on my '07 yfz which had an esr system onnit and running perfect,the scorpion recommended a 200 main as i have an open top with a k&n onnit when i did all this THE BLOODY THING WONT START,if you tow it it will only start if you pin the throttle wide open but as soon as you let go it stops again.will not spark or wet plug under normal cranking.is there a safety fuel/spark cut off onnit or what is going on pleaseeee help someone
200 main is waaaaay too big if everything else is stock. if your only mod is the "scorpion" exhaust then you should probably have about a 165 main and a 45 pilot. a good place to start on the fuel screw is about 2.5 turns out. whats your elevation?
'08 yfz 450 (non-fuel injected) Just put my DASA full exhaust on and FCI intake. DASA recommends 185 main and 45 pilot but they are out of Riverside / LA area. Well im up here in Reno NV (around 4500 ft) and not sure where to start jetting. Could use any advice you guys have thanx!

can some please send me the pics to the write up?
send to [email protected]
Hi guys Imo totally new over here , a couple months ago i bough a 05 yfz bone stock ...and know i just install a hmf slip on .... ok i know i need to rejet but i want to it right
my elevation its about 750 above sea level ( im in the east cost ) can be lower than that ..with the lip off and the hmf slip on will be 168m 45p clip #5 ?
and whit the lip on same but whit clip on #4 ?
im right ????

one more question right nw i have the clip on #3 position (stock ) do i relly need change the position of the clip to #4 OR #5 or i can keep it in the #3 position

thanks guys
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