Jetting problems w/ 07 YZ450F

Hey I am having a horrible time getting this thing jetted correctly. I have a new 07 450F. The carb looks the same as the 06. My question is does anyone know the stock (factory) specs and what I should change to. I am @ 4500 FT and temp usually is 60-90. Humidity is usually low 35% is all. Can any of you help out? Also I have the WB carbon pro exhaust.

Thanks

I'm running 48p/168main all year w./o issues on my '06. At your elevation I would thing the stock jetting might be pretty close. Try upping the pilot first then the main. :thumbsup:

Hey I am having a horrible time getting this thing jetted correctly. I have a new 07 450F. The carb looks the same as the 06. My question is does anyone know the stock (factory) specs and what I should change to. I am @ 4500 FT and temp usually is 60-90. Humidity is usually low 35% is all. Can any of you help out? Also I have the WB carbon pro exhaust.

Thanks

damn I would have thought after the lean conditions of the 06 they would have addressed this. What is the manual say for stock jetting settings?

What is the mj and pj in that 07 carb?

The PJ is 45 the MJ is 165 and the needle clip is #4.

Jet up on the pilot first after you try turning out the fuel screw. If you reach 3 full turns out then you need to jet up on the pilot. :thumbsup:

So quick question just to make sure I am thinking I am doing the correct thing. A 165 jet will let more fuel in than a 168 jet correct? And a 45 jet will let more fuel in than a 48 jet correct? And the needle a #4 lets in more fuel than the #3 setting? Am I thinking correctly?

Thanks for the help.

I think you have it backwards, the larger the number the larger the hole in the jet.

Equals more fuel or richer mixture.

The lower the number on the needle, less fuel. Needle at # 4 will be richer than at the #3 position.

The higher up the needle you go(towards #1 or top of needle), the needle will be allowed to be deeper into the jet thus leaning the mixture.

This is the way I understand it to be.

Ron

hey i know this aint about jetting, BUT HOW IS THE NEW BIKE treating ya? Any ride reports as yet?

I haven't really had a chance to really ride it yet. I hope to get it jetted and take it out this weekend. Stay tuned and I will let ya know.

The bigger the jet number, the higher the fuel flow EXCEPT .............on the leak jet. The lower the number on the leak jet the higher the flow. :thumbsup:

The bigger the jet number, the higher the fuel flow EXCEPT .............on the leak jet. The lower the number on the leak jet the higher the flow. :thumbsup:
Which makes perfect sense if you understand what the leak jet does. Just like the name says, it leaks fuel out of the accelerator pump discharge circuit. The bigger the number, the bigger hole, the bigger the leak, which, as you said, results in less fuel discharged at the accel pump spray nozzle.

But, the purpose of the leak jet is not to regulate the amount of fuel delivered, even though it gets used for that, as much as to control when it's delivered. If the leak jet did not exist, every opening on the throttle, no matter how slow or slight, would dump fuel down the carb throat. This is desirable when the throttle opening is suddenly increased, but when it is opened more slowly, it isn't. By putting a leak in the circuit partway up the vertical run to the discharge nozzle, fuel pumped upstream slowly will leak out through the leak jet instead of being pumped into the throat. If opened faster, fuel can't be leaked out fast enough, and it does get pumped into the air stream.

I haven't really had a chance to really ride it yet. I hope to get it jetted and take it out this weekend. Stay tuned and I will let ya know.

If you haven't ridden it, how do you know the jetting is off? :thumbsup:

The ignition timing and curves are different on the 07 vs the 06 so the 06 jetting fixes will most likely not be applicable to the 07 but I have the following jets in my bike.

48 pilot Fuel screw is out 2.5 turns at 1500 feet 80 to 90 Degrees temp

NFLR - 4

165 main

I have an aftermarket pipe and power nows with the TPS disconnected which is why I need more pilot jet.

The jets that are in the 07 may very well work but I think it will still be beneficial to get an adjustable fuel screw.

If you haven't ridden it, how do you know the jetting is off? :thumbsup:

good point....

:lame::p

Call the exaust company... I had to go to a 48 pilot jet for my DRD exhaust on my yz250F

Oh and next year we will have fuel injection and what will we do then?

I have ridden it just enough to know that it is off. Still working on the solution. Thanks for the replies.

What makes you think the jetting is off? Where is it missing on the performance scale? I have a hard time believing at your altitude and temp the stock jetting is not spot on. Did you ride it before you put the pipe on? If so how was it?

I didn't. I herd the 07 pipe cut low to mid power for the noise problem. So I replaced it.

First off I wouldn't always believe what you hear. That is a good way to waste $$$ as what is good for someone else may not work for you. Use a lot of the information here for a base line. If you have the stock pipe I would put it back on and take your bike for a rip. I think you will find the power will be extraordinary. Other than that, as stated, call the exhaust company and get a recommendation. Good luck

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