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Thread: Keihin 39mm FCR MX DRZ400 setup help needed

  1. #1
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    Default Keihin 39mm FCR MX DRZ400 setup help needed

    So after much research or attempted research I have worked out most kinks but am still having a few issues.

    Issue 1-
    When attempting WOT from idle it bogs out completely and shuts down. I can smell that it is too rich and from what I have read it sounds like its either too large of a pilot jet or the squirter action is injecting too much fuel. Will rev out well, but a quick wrap of the throttle to attempt WOT will kill it. Just not sure where to go with it. Should I also ry the o-ring mod first? I have read and understand that mod but looking at it and the functioning of the rocker it doesn't appear to separate where the o-ring would be needed. Ideas with any of this???

    Issue 2-
    Im not 100% certain that the current jetting is correct. But with all the info I gathered this is what I decided to run.

    Mods-
    3x3, Full Hindle exhaust, K&N
    Riding Altitude-
    6000ft - 8000ft, (Im also at the base of Pikes Peak and wouldn't mind having a jet setup to run that. That setting would be 8000ft - 14000ft)
    Current carb setup-
    main jet - 152
    main air jet - 200
    leak jet - 80
    pilot jet - 45
    needle - 3rd clip from top
    fuel screw - 2 1/4 turns
    note- most of these numbers are recommendations from a few different FCR setup threads I have read.

    Issue 3-
    I did take it for a quick test drive and it performed well, but at some point it just started dying between closed, 1/4 and 1/2 throttle. No sputter, hickup or anything like that. But it acted like it wasn't getting any fuel. Then it got to the point where it wouldn't even start at all. I'm not sure if it was because I was running it with the tank in the reserve position or not. I have the OEM gas tank petcock with the vacuum port but I haven't sourced the adapter that plugs into the bolt in the intake manifold. But I would think it would still run fine even set on reserve.

    Im pretty new to toying with carbs, but I understand the logistics of it. Just need a gentle nudge in the proper direction to get my gears turning. For now, I am stumped.

  2. #2
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    Go up on your leak jet. The FCR carbs are notorious for bogging off of idle when given a rapid WOT. You might also want to look into the R&D powerbowl, which will eliminate your issue altogether. Back to the leak jet. To go up in size, the numbers are backwards i.e. a 85 is smaller then a 80.

    You might also try going down a clip on the needle as well.

  3. #3
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    Quote Originally Posted by crash279 View Post
    You might also try going down a clip on the needle as well.
    By down you are saying go to clip 4 correct?

  4. #4
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    What needle are you using? I have a rmz450 needle in mine and that solved a lot of problems, but I'm also at 4400 ft.

  5. #5
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    Quote Originally Posted by whiskey_juliet View Post
    By down you are saying go to clip 4 correct?
    yes, move the clip down which will in turn move the needle up. Am I making any sense

  6. #6
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    Stock DRZ tank must be on PRI to keep it running without the vacuum adapter, reserve and On both use the vacuum.

    Moving the clip down will richen it, to lean it out, you move the clip up towards the top, contrary to what was said.

    So try moving it up a clip, so counting from the top of the needle you'd move it from 3 to 2, etc. If you get to the top, you need to go smaller on the pilot.

    For 6,000 to 8,000 feet Im gonna say you will probably need to go down a size on the pilot jet... 45 was good but just a tad rich when I was running it at 4,000. So at 6,000+, you should try something smaller.

    Do you know what needle you have? (The little letters etched in the side of it)

  7. #7
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    Quote Originally Posted by motokid23v View Post
    What needle are you using? I have a rmz450 needle in mine and that solved a lot of problems, but I'm also at 4400 ft.
    EMN needle.
    Quote Originally Posted by crash279 View Post
    yes, move the clip down which will in turn move the needle up. Am I making any sense
    You are making sense, I am just double checking.
    Quote Originally Posted by calco88 View Post
    Stock DRZ tank must be on PRI to keep it running without the vacuum adapter, reserve and On both use the vacuum.

    Moving the clip down will richen it, to lean it out, you move the clip up towards the top, contrary to what was said.

    So try moving it up a clip, so counting from the top of the needle you'd move it from 3 to 2, etc. If you get to the top, you need to go smaller on the pilot.

    For 6,000 to 8,000 feet Im gonna say you will probably need to go down a size on the pilot jet... 45 was good but just a tad rich when I was running it at 4,000. So at 6,000+, you should try something smaller.

    Do you know what needle you have? (The little letters etched in the side of it)
    Good info, I agree with going to clip 2 on the needle, seems rich on 3rd.
    Good to know about reserve and on being vacuum operated. I will eventually do the vacuum mod.
    I was thinking of starting with a 40 pilot instead of the 45 thats in it. I think the accelerator pump is possibly putting out too much fuel in the shot, anyone know of a write up on how to adjust it. I know its possible but I havent seen a how too. I know the trick of recording it with a camera at 30 frames per second, but the adjusting it is stumping me.

  8. #8
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    Id recommend trying a 42 before the 40.

    To adjust the AP, there is a screw that sits on the plastic rocker arm, if you get your carb out and look at it, it should be pretty clear. I never touched mine, but im told a quarter turn makes a huge difference.

    I wouldn't start playing with that until you go down on the pilot. Im almost positive that's your problem, unless you got the FCR from someone else who had adjusted the AP.

  9. #9
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    Quote Originally Posted by calco88 View Post
    Id recommend trying a 42 before the 40.

    To adjust the AP, there is a screw that sits on the plastic rocker arm, if you get your carb out and look at it, it should be pretty clear. I never touched mine, but im told a quarter turn makes a huge difference.

    I wouldn't start playing with that until you go down on the pilot. Im almost positive that's your problem, unless you got the FCR from someone else who had adjusted the AP.
    The guy I got the carb from had someone else tune it for him. I will do the pilot first, pick up a 42 and a 40 just in case.

    I am familiar with where the rocker is. And I will leave it be for now to see if adjusting the pilot and needle fixes the issue.

    Otherwise my jetting should be good for what mods i have and the altitude im at?

  10. #10
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    Yeah the rest looks pretty good to me. I'd say you have a good starting point once you get that 42 in there and start at 3rd clip and begin the fun process of fine tuning.

  11. #11
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    Quote Originally Posted by calco88 View Post
    Yeah the rest looks pretty good to me. I'd say you have a good starting point once you get that 42 in there and start at 3rd clip and begin the fun process of fine tuning.
    I might try to bring it up to Eddie Sisneros. He is about an hr north of me. Figure I will do the hard stuff then see if he will make it nasty. I also have Stage 1 hot cams ready to go in as well.

  12. #12
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    The EMN needle is your issue with it cutting out just off idle. I live at 1800ft. and ride up to 5500 ft, and the EMP needle fixed that issue for me.
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    "Just stay in the fast lane, and keep moving, you cannot predict your final day, so go hard for the good times while you can." Kenny Stabler
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  13. #13
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    Quote Originally Posted by HPIguy View Post
    The EMN needle is your issue with it cutting out just off idle. I live at 1800ft. and ride up to 5500 ft, and the EMP needle fixed that issue for me.
    Ah, I see. And agree. If you look on the link I post it shows almost exactly what I followed to tune the carb. But while looking at the recommended tune settings I didn't notice the the small change from EMN to EMP due to elevation. Wonder if my parts store here carries any of those. Guess I will have to wait till tuesday.

    http://www.drzparts.com/2010/05/dr-z...-carb-install/

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