Jetting help please

91 replies to this topic
  • Stealth13

Posted February 04, 2012 - 08:49 PM


Finally got the bike running and it runs great up to about 80 percent throttle . Once I go 100 it stutters like there's not enough fuel going in. It has the grey wire and yz stop done. Does it need a richer jet to compensate for this change?

I was told I need a special tool and I can get the one jet from the outside without taking anything off.

  • W R

Posted February 04, 2012 - 09:32 PM


What is your bike?
Do you still have the stock exhaust?
If it is stock have you uncorked it? If not you will want to!
Did you leave the snorkel in?
What altitude do you ride at?

Long story short I will say yes you will want to rejet your bike if you have not done so. You will not need anything special and you should be able to do everything you need to with out removing the carborator. It is a little bit of a pain in the ars but definitely possible.

With out answering all of your questions there is one sure fire way of getting your bike jetted correctly. Purchase a JD Jet kit. They are a spendy at around $85 but it will come with all of the jets and needles for your bike. It will give you step by step instructions how to get to your carborator, what jets, to use, what needle to use with the clip at ???? groove depending on your situation. Basically it is fool proof. Just got done jetting my bike and it was on the money the 1st try by following JD's instructions.

Many people on here will agree to go with the JD kit and many others will say just buy the exact pieces you need at a 1//4 of the price. If you are like me I don't mind getting a few extra pieces I will not use just for the convienence of getitng it all at once.

Also, the JD kit will come with the o-ring to put on the eaccelerator pump timing adjustment screw for quicker throttle response.

I don't know if any of this helps but it is a start to your thread.

  • wrwest

Posted February 04, 2012 - 10:10 PM


Just fit a larger Main jet as it works at the top end of the rev range .

  • Stealth13

Posted February 05, 2012 - 12:11 AM


Its a 2006 wr450 , can I get at the main jet from
The bottom of it? How hard is it to swap if I've never done it?

  • MANIAC998

Posted February 05, 2012 - 06:11 AM


Yes, you can reach the main jet from the bottom of the carb, thru the 17mm carb nut opening. And it is probably the easiest one to get out. But that doesn't mean it's easy! It is do-able though. Maniac

  • Stealth13

Posted February 05, 2012 - 08:10 AM


Do you guys think doing the main jet only would fix my full throttle stutter?

  • Bandit9

Posted February 05, 2012 - 08:37 AM


Probably, that along with the YZF needle or JD needle. Your pilot needs to be correct as well.

  • wrwest

Posted February 05, 2012 - 09:58 AM


Sounds like its only the main causing the problem if its from 80 % throttle

  • Stealth13

Posted February 05, 2012 - 10:16 AM


Ya like 80 percent throttle is fine and after that it stutters. So just replace the jet that I can access from the outside with 17mm wrench ?

  • Bandit9

Posted February 05, 2012 - 11:03 AM


Yeah on the main, big nut on bottom of bowl, I think the main will require a 6mm socket.

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  • Stealth13

Posted February 05, 2012 - 11:17 AM


How hard is it to do if I've never done it/ have no idea what I'm doing?

  • MANIAC998

Posted February 06, 2012 - 08:58 AM


It's not difficult to do. Like Bandit said, you'll need a 6mm socket to remove the main thru the bottom of the carb. Maniac

  • Stealth13

Posted February 06, 2012 - 10:46 AM


Got all the tools, what jet should I get ?

  • Stealth13

Posted February 06, 2012 - 11:38 AM


My elevation is 3500 feet or 1000 meters above sea level

  • MANIAC998

Posted February 07, 2012 - 05:01 AM



  • Stealth13

Posted February 07, 2012 - 07:15 AM


I'm in Calgary so I ride anywhere between 0-35 degrees Celsius

  • Leardriver

Posted February 07, 2012 - 01:44 PM


162 main jet for $6. Save your money vs a kit.

Changing a main jet can be done in 3 minutes if you are fast, just as a measure of complexity.

Shut off gas at the petcock.

Loosen the hose clamp thingies that hold the carb tight in the rubber boots. One on each side of the carb, intake side and airbox side.

Twist the bottom of the carb out towards the left side of the bike. Remove the 17 mm bolt on the bottom of the carb. An ounce of two of gas will come out.

Look up in the hole where the bolt was, and see the jet. It should match the one you are going to put in. Remove gently with a 6 mm socket and 1/4 inch drive. Put the new one in, and tighten very gently. Barely snug.

Reinstall the 17 mm bolt, twist the carb so that it is straight up and down. Tighten hose clamps, turn gas back on, and see if it runs better now.

In the summer, put a 160 main jet in.

  • Stealth13

Posted February 07, 2012 - 01:59 PM


Thanks a lot, what is the stock jet size? Higher number is richer right ?

  • MANIAC998

Posted February 08, 2012 - 06:13 AM


Stock is 165. I'm thinking you need to go up to a 172, or at least close to that size (170 or 175). And yes, a higher number is richer. Maniac

  • Stealth13

Posted February 08, 2012 - 07:11 AM


Why is one of you saying 162 and the other 172. Wouldn't 162 make my issue worse if 165 is stock ?


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