05 CRF 450 Jetting problems with JD Kit

Took out my new bike today for the first time. It was a bear to start and once started it poped and backfired like crazy. It was also cutting out a bike out with a quick chop of the throttle and basically ran really lean. It came stock with a 168mj.

Before I ever even started the bike I put the JD Kit in. I also put in the zip ty screw and the Twin Air screenless filter kit. THe JD Kit calls for the Red needle in the 5th position from top. It also called for a 178mj at my elevation 0-3000 ft. Temp today was around 70-80. I put in a 180mj when I got home and it helped some with the backfiring. I also tightened my Zip Ty Screw to try and help the cut out when I chop the throttle. There were too other guys at the track with stock jetting who had no complaints on their new 05. Anyone have any ideas what I should try? Would lowering the clip on the needle richen it more than a bigger mj? Its kind of like I am rich in the pilot and lean in the main??? Not sure where I am at with the needle. Thanks guys! Help JD!

Put back in the stock needle and a 170mj to compensate for the screenless filter (168 is stock) and the thing runs like a champ. No popping or backfiring whatsoever. I also got rid of the downlow bog with the zip ty screw. Wonder if the JD Kit for the 05 still needs some fine tuning? James, do you think you could help me fine tune your kit to run better than the stock settings?

I'm lost. I have a stock '05 CRF450. I live in California where it currently is between 65-80 degrees. Where I ride is about 500 feet of altitude. I tried the JD and the TY fuel screw and all I get is backfiring on deceleration, which would show lean. I played with needle clip settings and the fuel screw, but was unable to eliminate the popping. I went back to stock and minimal popping if I run a 170 main, and about 2 turns on the fuel screw.

Once the weather changed with the recent rain, I was all screwed up.

What is your recomendation with the JD kit at my settings? I know someone said the red or blue needle can give different power types, and suggested a good setup, but I could not find the post.



The Blue marked needle is less likely to pop on deceleration. The Blue needle in the 3rd from top clip position is a good alternative to the red in 5th from top. When I was testing the CRF450R, either of these needles and clip positions worked as well. The YZ450F will also run blue #4, which is richer thru most of the range.


That's odd guys because I'm having the same problem and can't figure it out. This is what I have and what I've tried. I have a full dr. d pipe with screen removed from filter cage and a zip ty fuel screw. I'm in arizona and ride between 500-2000 elevation. I tried the 175mj, and red needle 5th position and popped a lot on deceleration. Then I tried the Blue Needle 3rd position and 175mj, and much worse, popped like crazy and sputtered a bit on acceleration. Put back the red needle 5th position and tried a 178mj and also tried a 172mj and no luck at all. In the meanwhile I played with the fuel screw like crazy lean to rich with 1/4 turns. I can't figure it out. It does not seem that I have any exhaust leaks. My thoughts are similar to the first but not sure, it seems that the bottom end is lean and the top end is rich. Any more suggestions would be helpful. Please let me know when you get it figured out because I really want this baby to run like a champ not a chump. :cry:

I am glad to see I am not alone here. Like I said before I put back in the stock needle and 170mj and have the fuel screw just under 2 turns out and it runs great. I also found that with JDs red needle in the 5th position and a 180 mj I didnt have as much popping. All I know is I put in the kit before ever starting the bike with a 178mj and a red 5th position and went to the track. It was a miserable day. Backfiring and popping all over! There were two other guys out there with 05s and stock jetting and there bikes ran and sounded great. I think I will leave my stock settings in till someone gets it dialed in. By the way, how do you like the Dr. D pipe? I am Arizona also riding at the tracks around PHX so we have the same setup minus the pipe...

JD. Do you think if we went up one size on the pilot jet it would help? I was never able to get the fuel screw right, and maybe because it was overal too lean.

Millerman, That's what I was wondering on the pilot jet as well.

MXfever, On my '04 I like the pipe and on my '05 I haven't been able to get my jetting right. I just got back from the dunes even though the bike wasn't running perfect, still had a blast. Maybe i'll meet up with you at the track sometime and you can give it a whirl. Doesn't make huge increases but does make pretty good mid power.

I went to the 145 pilot and 170 main with the Twin Air filter w/o the screen, stock pipe. When I finally adjusted the fuel screw by turning up the idle to ~ 2ooo rpm and turning the fuel screw to the point of highest RPM, the bike ran great and did not back fire any longer. My dealers parts guy said the 05's are lean.

The red marked needle is close to a stock needle at low throttle and should not have problems. Was your original needle NCYR in clip position #3?

You could try the #45PJ, as it came stock in the first CRF450 with no issues.


James, Stock needle is in the 4th position from top. Are you saying to try the following:

Red needle in the 5th position, 175mj and 45pj?

I agree, sounds like you need to up your PJ one step. Especially if you are already 2.5 turns out on the fuel screw. The PJ should clear up the decel popping if you richin it one step.


The YZ450F uses the blue marked needle in the middle (#4) position. Based on the descriptions, a richer low-end is called for which would be Red #6, 2 turns out.

The main jet should be 2-3 steps bigger than stock, or a #175.


Not sure about the ncyr but it was in the 4th position for sure

I think I have it almost figured out.

I went to a 45 PJ, red needle #5, 178 Main. It was close, and only minimally popped if I ran the air screw about 2.25 turns.

I switched to the blue #3 with the same other jets, and with the air screw at 2 turns, I have almost no popping. The bike pulls strong and is smooth. Not hits, or bogging either.

Disclamer, so far, I have only been able to try it near my home, not on a track or real trail riding, so it still may need to be adjusted further. I think it would only need fine tuning with the fuel screw, though.

JD, is the blue 1/2 size richer than the red on the low end? That would explain how it was acting.


James, The needle on my 05 is a NGGQ

The blue needle is richer on the straight diameter as well as the taper (clip position).

The NGGQ is new for '05.



James, Can you please give us a set up to use for the 05. Sounds like your kit was based on a different needle than what actually came with the bike? From what I can piece together here is what we should use:

Red 5th or Blue 3rd

42 or 45 pj

175 or 178 mj

I can tell you that red 5th, 42 pj and 178mj runs terrible. Can you please give us an exact setup to try?


Try the following jetting-

#42PJ (stock)

2 1/4 turns out

Red #6 or Red #7

#175 main jet

This is closer to the YZ450F jetting.

The next choice to reduce popping is blue #4 or a #45 pilot jet.

Note-Aftermarket pipes sometimes pop on deceleration more than stock. They must be completely sealed at the head and muffler flanges to keep the popping down.

If you're using the aftermarket fuel screw, make sure the spring, washer, and O-ring were all installed correctly. The low speed jetting will be off if they are not.

Turn the fuel screw outwards to richen the low-end. Do not hesitate to use a richer clip position, blue marked needle, or turn the fuel screw outwards. The '05 CRF is using a richer setting at low speeds.



If any CRF450R owners are having problems with the kit jetting- please post, send a PM, or send an email to me directly for specifics regarding your bike and setup. I will make sure you are completely satisfied.




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