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Jetting Suggestions???????


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I own an 07 CRF450X and I live and ride in between 5500 and 7000 feet. What Main, pilot, and leak jets do you recommend and how many turns on the fuel screw. I know this probably belongs in the carb forum, but I figured I would get a CRF450X specific answer in this forum. Thank!

I suggest you buy a jetting kit from JD Jetting. It has information for fine tuning at your altitude, Accelerator pump tuning, airbox mods, exhaust mods, etc.

You can't just change one thing and hope for an improvement. It's all connected.

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In my opinion, may as well open the air box since there is a pipe on there. That will help you reap the full benefits of it. Im at a similar altitude in Colorado, 5-8k ft riding. I have open air box, full exhaust and stage 2 cam. 165 main, ncvs needle 3rd down from top(i dont recall my pilot but it may be stock). That seems to be a hot ticket. My brother has similar setup but is running a 162 main and ncvs needle.

Stock main is 142 I think, so yeah rich. If you go into a shop and tell them you want a 165 or even 160 for your 450x they may scratch their head over the fact is sounds rich but consider these bikes come lean from factory. The Honda dealership basically laughed at me when I told them what jet for what bike I needed, funny thing about it was the bike absolutely hauls ass compared to stock form. Spark plug looks perfect too.

All of the jet settings I have tried have come from the 450x forum.

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Definitely richer on the main. The X is a 50 state legal bike and literally the only way they could get it to pass emissions is to stick something up its butt (see stock exhaust tip) and reduce the amount of fuel going into the engine.

Not only do you need to go richer, you need to go way richer. This bike will come alive. Plus running a bike lean can burn the engine up.

FYI... the R does not have to deal with this as its a closed course competition bike so it does not have to meet the EPA standards of a 50 state legal bike

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I'm headed to cloudcroft this weekend for riding. Here's the jetting specs I've been using for quite some time with great success.

Year: 2007

Elevation: 8000-12000

Temperature Range: 30-70 degrees

Smog (AIS): removed

Airbox Modified Top: cut

Airbox Modified Sides: cut, and 1” holes drilled

Backfire Screen: stock

Air Filter: stock

Pilot Jet: stock (42)

Main Jet: 162

Needle: JD jetting red

Needle Clip Position: 4th (may try 3rd)

Fuel Screw Type: R&D adjustable

Fuel Screw Setting: 2 turns out

AP Modified: merge spring

Leak Jet: 55

AP Cover: stock

Exhaust Type: MRD full

Exhaust Modified: no

Pink Wire Modified: no

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All good stuff, more validation of what your doing & some tips.

Here is my setup.

Year: 07

Elevation: 3000-6500

Temperature Range (°F): 30-90

Smog (AIS): Removal Kit

Airbox Modified Top: Yes Snorkel and some top

Airbox Modified Sides: Right Side only (problably wouldnt do it again)

Backfire Screen: Installed

Air Filter: Twin Air

Pilot Jet: 48

Main Jet: 170

Needle: JD Red

Needle Clip Position from top: Middle

Fuel Screw Type: t handle

Fuel Screw Setting: 1.5 out

AP Modified: Yes Merge Racing spring

Leak Jet: 55

AP Cover: ...

Exhaust Type: stock

Exhaust Modified: Baffle removed (spark screen still in)

Pink Wire Modified: No

As Krannie mentioned so much of this is related it makes since to try and do stuff at the same time.

Be sure and change your leak jet, if not you will have bog. Since your changing your leak you have to pull your carb, no way around it on the 07. Since your pulling the carb you might as well put the merge racing spring on the AP, and order yourself the merge racing carb allan screws & ditch the crapy phillips head ones.

IMO this is what needs changed at the same time: Main, leak, Pilot/slow, AP spring, needle, open air box (at least top) open exhaust, fuel screw.

The JD kit will contain the Main, pilot, & needle, dont mess with the orings get the merge spring as mentioned. JD instructions are great.

Dont know how technicaly you are but pulling the carb isnt that bad. If youve never done it take alot of pictures and your digial camera of hose routing. And give your self some time.. be sure everything is really clean. bla bla bla

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Okay, got my carb off and checked all the jets. The main is a 152, Pilot is 45 and I have a Boysen quickshot 3 AP cover and the needle is stock. There is another small jet by the main and pilot jets, the number on it is 70. Can anyone tell me what the hell that is? I can't find it anywhere in the Owners Manual. I have to add that I am not the original owner of this bike, the previous owner must have changed the main jet because 142 is stock. My JD Jet kit should be here tomorrow afternoon, so here's what I have so far:

Year: 07

Elevation: 5500-8000

Temperature Range (°F): 30-100

Smog (AIS): Removal Kit

Airbox Modified Top: Yes, Snorkel and some top

Airbox Modified Sides: No

Backfire Screen: Spark Arrestor

Air Filter: Stock

Pilot Jet: 45

Main Jet: 152

Needle: Stock

Needle Clip Position from top:

Fuel Screw Type: Aftermarket adjustable

Fuel Screw Setting: 1.5 out

AP Modified: Boysen Quickshot 3

Leak Jet: 1 1/4 turns out (55)

AP Cover: Boysen Quickshot 3

Exhaust Type: Big Gun Quiet (slip on)

Exhaust Modified: No

Pink Wire Modified: Unknown

Thanks for the help guys!!!!!!!

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ok you have your main 152, your pilot/slow45, and then the mystry 70... Im guessing that is your leak jet as that (70) is what comes stock on your bike.

A picture would help...

Ive never seen a boysen installed so maybe Im wrong

Try this... sorry but I forgot which specific model the carb is... Ill see if I can find it....

http://www.sudco.com/Carburetor01.html

I think its the FCR for MX...

the other link I posted and deleted didnt show the right carb.

... yeah that looks pretty good, from there you should be able to figure out your mystery jet. Let us know if not...

Edited by 4rideon
update
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Year: 07

Elevation: 3000-6500

Temperature Range (°F): 30-90

Smog (AIS): Removal Kit

Airbox Modified Top: Yes Snorkel and some top

Airbox Modified Sides: Right Side only (problably wouldnt do it again)

Pilot Jet: 48

Main Jet: 170

I have had a couple people tell me i was crazy for putting in a 48 pilot at 5000 ft but it is obviously working for you too! the same person also told me a 170 was way too rich for my altitude but anything leaner and the bike runs funny.

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I have had a couple people tell me i was crazy for putting in a 48 pilot at 5000 ft but it is obviously working for you too! the same person also told me a 170 was way too rich for my altitude but anything leaner and the bike runs funny.

Yeah I had crazy bad bog on my 07 and overheating problems. :eek: I started leaner and then ended up with what Ive posted. I believe it was a 162 on my main and slowly worked my way up.. I was pretty discuraged with my jetting problems. Lots of trial and error & I think bikes sometimes just act a little different from one another. Ive been running this same setup for over a year now and no problems. The bog is a thing of the past. :banana: Starts good, idles good, and rips. :ride:Not sure of my exact range, but Ive put on some 60 mile rides lately and havent hit reserve, although looking in the tank it must be close.

The main is pretty easy to change, maybe start with a 165 ? but I wouldnt try any lower then that youll just be changing them out.

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