[jegarner]

2007 CRF450X Riding@ 2000' to 7000' with completely stock bike.

I recently won an FMF Power-Up Jet Kit # 012611 and purchased an FMF exhaust pipe as well. I really want to install both of these since the bike stalls frequently on deceleration in stock form.

However, I've been hearing a lot about the JD Jet Kits and wish I had one that instead, but since I'm on a tight budget, I'll have to use the FMF jets.

Since I ride at different altitudes frequently, would I be better off with the JD kit? Maybe I can purchase one later on........

As for now, I'm going to try the FMF jet kit using the main jet # CJ132 (3000'-6000"'). Specs say to set the needle at #3 from the top and the mixture screw at 2 turns.

I haven't done much carb work in the past, but re-jetting looks pretty easy, I', just not looking forward to the misc adjustments to get it running correctly.

Any helpful advice out there regarding this?

[450xdirt]

Make sure you cut your air box to get more air in (mandatory). Also buy an aftermarket fuel screw it will help to dial it in. I like the R&D flex screw.

I'm not familiar with FMF kit but I would go with the main jet one step bigger.(JD 168 or 170) and richen up that needle 4th from top.

I'm sure someone else here has used the FMF kit and will know how it compares to JD. Jetting is easy so if it does not work the first time you can change it and try something else.

My spec. are in my garage to compare.

[jegarner]

The jets that come with the FMF kit are CJ128, CJ132, CJ136, CJ140 and CJ144. Since I haven't re-jetted a motorcycle yet, by going one step bigger would be the CJ136 I assume. Are they marked on the jets,

I'm not at home right now, so I can't take a look at the jets until later....

Also, I haven't entered any info in my 'Garage' on this forum, but I will take a look at yours and update mine tomorrow when I have more time.'

Thanks for your advice.

[450xdirt]

Yeah I'm not sure about those main jet #'s, they seem awful small to me. Most guys here are running 165-180 mains.

Maybe FMF has different numbers for the same size jets?... I'm thinking that they don't and the jets that you have are just small. BUT don't take my word for it see what FMF says, or maybe some one here knows.

[jtsurfs]

Yeah I'm not sure about those main jet #'s, they seem awful small to me. Most guys here are running 165-180 mains.

Maybe FMF has different numbers for the same size jets?... I'm thinking that they don't and the jets that you have are just small. BUT don't take my word for it see what FMF says, or maybe some one here knows.

I was thinking those jets sound pretty small. I agree with 450xdirt, check with FMF about those jet sizes.

[jegarner]

After checking with FMF, they mentioned that these jets were provided by Dynojet and the size I listed in the previous post are correct (128, 132, 136, 140, 144).

Now I'm somewhat worried since a couple of posts mention that they should be in the range of 165-180.

I guess once I get them installed (sometime in the beginning of next week), I will submit another post to let you know if they work..........

[bamm]

from what ive learned the size of the main jet varies largely based on the taper of the needle. example, with jd jet kit im running a 180 main jet because the jd needle has a leaner taper than stock thus allowing the larger main jet. i would just follow the instructions that came with the kit for your bike and conditions, i bet it will be close to if not spot on. if it doesnt work go from there, but its important to remember that a jet kit is not just an assortment of jets. the jd, and fmf(dynojet) are engineered and tested, to work in accordance with the needle and main jets included in the kit,so you cant really compare the sizes of jets to someone running a stock needle.

[450xdirt]

from what ive learned the size of the main jet varies largely based on the taper of the needle. example, with jd jet kit im running a 180 main jet because the jd needle has a leaner taper than stock thus allowing the larger main jet. i would just follow the instructions that came with the kit for your bike and conditions, i bet it will be close to if not spot on. if it doesnt work go from there, but its important to remember that a jet kit is not just an assortment of jets. the jd, and fmf(dynojet) are engineered and tested, to work in accordance with the needle and main jets included in the kit,so you cant really compare the sizes of jets to someone running a stock needle.

Bamm is right. Do what FMF tells you and then go form there.

Does that FMF kit come with a needle?

[jegarner]

After looking over the FMF jet kit, it appears that I'm replacing only the main jet and fuel needle, and the stock pilot jet stays put. Is this the same with the JD jet kit as well.

I thought I would be replacing both, but since this is the first time I have replaced the jets, I'm not sure.......

[450xdirt]

Yeah same a JD. your stock pilot should be a 45 and will do fine for you.