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czechalien

Jetting 2009 YZ450 how to

14 posts in this topic

Just got my aftermarket exhaust and need to re jet and raise the needle one click.

Never done it before any suggestions ?

THX

You need to install a 48 pilot, install the clip on the needle fourth from the top(stock is 3), 165 main jet. This will be good for all cnditions up to about 7 or 8k elevation.

Either read your owners manual or take to someone that knows how.

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Just got my aftermarket exhaust and need to re jet and raise the needle one click.

Never done it before any suggestions ?

THX

Why do you think you need to do any of that?

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To get to the carb, you will need a young priest and an old priest.

Good luck, do a search, I posted something about getting to the carb two weeks ago and got some great suggestions from the guy's here including grayracer.

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I am about to do this as well. Just got a fmf 4.1 megabomb system for my 09 yz450. Your going to have to take off the shock, plastics and gas tank to get to the carb. There may be enough room to change the main without taking it out but then again I havent really looked at it that hard and it looks pretty cramped in there. From what Ive heard 165 main seems to be a must, I havent looked up the rest, I hope this thread keeps going so I dont have to look!

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I didnt need the pilot change or the needle adjustment...just added the 165 main and it runs great. I just adjust the fuel screw as needed.

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I'd still like to know why he thinks all of the changes he lists are necessary.

But, as to carb access, the main AND the pilot can be changed through the bottom without rotating or otherwise disturbing the carb. The main is easy (as long as the jet holder doesn't unscrew off of the needle jet), the pilot is a little more challenging, but very doable:

http://www.thumpertalk.com/forum/showthread.php?t=556427

To change the needle position, remove the seat, tank, and upper engine mounts and the top of the carb is much easier to access. Some people insist that they can work around the mounts, but I find it faster and less annoying to just get them out of the way.

All of that can be done without even loosening the carb. If you want to remove it:

  1. Remove the seat and the muffler.
  2. Unbolt the air box from the sub frame (two bolts on top behind the gas tank and the two lower rear fender bolts)
  3. Unbolt the sub frame and slide it back off of the air box.
  4. Loosen the air boot clamp and remove the air box from the carb

The carb can be removed now. Disconnecting the top of the shock and tilting it back does make it simpler, but it's optional. Reassemble the air box to the carb and then install the sub frame in the reverse of the order above, and you'll find the air boot is much easier to deal with than by any other means.

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He probably just read someones post on here where they did the same and then raved about it...if he is around sea level, he doesnt need the pilot or needle change.

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can't really find anything about jetting 09YZ450F I just installed FMF Powercore 4.

I'm pretty new at this so I'm not sure if I have to re jet or not, but seems like Grayracer513 thinks I don't have to and he is smart when it come to YZ's.

I live in Atlanta.

THX

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Here you go. http://www.thumpertalk.com/forum/showthread.php?t=887645

Since I intend to buy a new silencer for mine as well, my plan to install it, and then see how it runs. I really do not want to have to tear into my bike to jet it unless I absolutely have to. Have you installed an aftermarket air/fuel mixture screw yet? If not, that would be the first thing I'd buy before worrying about jetting.

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can't really find anything about jetting 09YZ450F I just installed FMF Powercore 4.

I'm pretty new at this so I'm not sure if I have to re jet or not, but seems like Grayracer513 thinks I don't have to and he is smart when it come to YZ's.

I live in Atlanta.

THX

You don't always arbitrarily need to rejet the bike for a change of pipe. I'd suggest you first read this one:

http://www.thumpertalk.com/forum/showthread.php?p=2881699#post2881699

Then look through these posts for similarly equipped '08's or '09's to see what others have done with them:

http://www.thumpertalk.com/forum/showthread.php?t=694918

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