The XR400 Thread

Discussion in 'Thumpers' started by Hayduke, Jan 16, 2008.

  1. amockalypsenow

    amockalypsenow dirtybiker

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    anybody have a 96 or 97 cdi for sale? dm me please.
  2. SkolBerts80

    SkolBerts80 n00b

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    Wow this thread is insane, 677 pages!

    I bought a 2000 XR400 this spring. I took it to a buddy of a buddy who is a full time mechanic out of his garage to go through the entire bike and get it ready for the season. He rebuilt the carb and it would start in 3 kicks every time cold. When hot its always first kick, even if I drop it it fires up in a couple kicks without the decomp. The more I rode it the harder and harder it got to cold start. I'll admit I did run ethanol gas in it. Since I have drained the gas tank and ran enthanol free only from here on out. I was assuming that was the cause. I took the carb apart last night and it looked pretty good in there. The numbers off the jets were 142 & 526 if that makes sense. It ran perfect before so the jets seem correct. I live in Boise so I ride elevations from 2500 to 10000. I got it to fire but it will not idle. I have messed with the idle adjustment screw so much I'm not sure where it needs to be, anyway to find that out? Seems like the screw isn't doing much, all the way out or in and she acts pretty much the same. Before I disassembled the carb I checked the lean/rich screw on the bottom of the carb and it was about 1-3/4 turns out. I set it for that which should be correct from the research I've done. Some people say you can go out to 2-1/2 but that should be max, anymore and a guy needs to rejet. I also noticed I do not have the "cone" or "skirt" that is the carb, its the yellow thing you should see right away when accessing the bowl.

    Any recommendations? Should I keep playing with the idle screw and the lean/rich adjustment? Maybe I should order that skirt thing? I'm not sure what it does but it ran fine without all summer.

    Thanks for your help!!

    Edit, Maybe I should buy the Pumper Carb from XRonly.com and be done? Its spendy but I have heard amazing things about it. If its a game changer it might be worth the $400 or whatever. Although I have read they are way more complicated, might be over my head.
  3. molnar.b

    molnar.b Adventurer

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    Hey,
    I suggest that you should take off the carb completely, or at least take out the jets and clean them out. Even if you don't see any residue/junk from the ethanol it could be there. Blow out the air passages on the jets (plus the thing the main jet threads into - I don't know how it's called in english), or put it in a ultrasoniv cleaner if you have one.
    The jets: well, I have to admit that I chuckled a bit when I read the 146/526 part :D the 146 is you main jet, the other is the slow/idle jet it should be between 50-60. Jetting is a tricky thing, I'm no expert in it so be cautious with my advice. If you have a completely stock bike IMO those jets should be fine. But if the Gordon mods have been done to the bike (no airbox snorkel, the welds in the header have been grinded, a less restrictive air filter and so on) jetting must be corrected. Some guys here run 162/62, 160/60, me (and I think shinyribs too - not sure on that one though) 158/55. You have to find out what suits your riding style and elevation the best.
    Check the spark plug, it should tell you if the jetting is way off or roughly good. The idle screw should be between 1,5-2,5 in general, but this depends on your jetting and elevation and everything! Set it to a position where the bike feels happy.

    Also, there is an index thread, where you can find lots of useful information about these bikes.
    Good luck with it and have fun
    Stretch67, cmbthumper and shinyribs like this.
  4. SkolBerts80

    SkolBerts80 n00b

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    The 526 doesn't make sense to me either. Maybe its 52 but there is another number after it, its hard to read. Either way it ran perfect before with those jets. My bike it stock, no mods have been done. Since I had the carb off I did pull the jets to clean them and blow them out. I cleaned the bowl and floats as well but that was about it. I didn't take it apart any more than the bowl area. I'll check the spark plug, start over with the lean/rich screw and hopefully can get it to idle. It rides nice, just won't idle. Do those idle screws get messed up from time to time? The spring doesn't seem to be doing much. Maybe I need to take it apart again and go through it more but it looked really good inside.
  5. molnar.b

    molnar.b Adventurer

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    As far as I know that little spring is just for tension so the screw wont back out. Theres an o-ring in there too, make sure it's actually in there.
    Check the float height too, it could do weird things to the bike. Maybe a new spark plug would be nice too.
    shinyribs likes this.
  6. molnar.b

    molnar.b Adventurer

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    Or just adjust the idle screw (not the mixture screw!) near the top of the carb :D
  7. SkolBerts80

    SkolBerts80 n00b

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    I was playing with that last night, its to the point now that I have no idea where to start. I was going all the way out and all the way in and it didn't seem to matter. Is all the way out a higher idle? Seems like a good place to start. Slowly lower it down from there. If I can get the thing to idle even very high I'll be happy as I can take down. Sounds like I just need to trail and error it back to health.
  8. molnar.b

    molnar.b Adventurer

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    All the way out is the lowest idle. If you're turn the screw clockwise it will increase the idle if I remember correctly
    shinyribs likes this.
  9. shinyribs

    shinyribs Thumpers for life

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    Since the bike was easy to start before, i wouldn't change anything in the carburetor. Like Molnar said, would be a good idea to clean the jets- especially the pilot jet. The pilot jet is small and will gum up easily. Main jets typically never gum up unless something severe happens.

    You're gonna be shooting in the dark setting the idle speed screw now. Your best bet is gonna be to look at the slide ( viewing from the air box end ) and raise the slide with that screw until it's about 1/8" up off the base of the carb throat. That should give the bike enough air to run without running away from you.

    For the reason of slowly becoming harder to start, I would check the valve lash. When they get tight the bike doesn't like to start. A really simple thing to check is strength of your spark. If it's not bright blue, unscrew the plug boot from the wire and see if the connection is dirty. You can do that in about 1 minute with no tools.
  10. SkolBerts80

    SkolBerts80 n00b

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    This is a good learning experience. I should have started with the plug to begin with, start with easiest right. I should have checked the valves when I have the carb, seat and talk off last night. If the plug looks good I'll pull everything and make sure we are good. Good news is these bikes are pretty easy to work on and I'm getting more intimate with my XR which I like.

    How often do the valves need to be checked? They were checked 400 miles ago. At the same time carb rebuilt and new plug was installed. Maybe it was running rich and was semi fouled my plug.

    Thanks for all your help! I'll update once I get the time to go through the bike again. My deer and elk hunting season starts tomorrow so time is going to be an issue.
    molnar.b likes this.
  11. mkn

    mkn Been here awhile

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    Well I got sick of the stock headlight even with the full charging system I have because of the e-start I just could not find anything worth a damn

    I like the stock headlight fairing and wanted to keep it. So I took a leap and found these 75 watt off road lights and they happen to fit nice and snug in the opening either from the front or in the back as well.
    I opted to install it from the front and I was able to us my headlight guard to hold it nice and tight.
    If your creative you can definitely fab up some brackets to mount it up to the stock fairing.
    I am very happy with these and they only cost me 27 bucks shipping through Amazon and a bonuses I got 2 so if one goes bad I have a replacement. IMG_20191007_151335.jpg IMG_20191007_162741.jpg IMG_20191007_192126.jpg IMG_20191007_192159.jpg
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  12. BSW

    BSW Been here awhile Supporter

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    Nice lights any more info on these.
  13. Stretch67

    Stretch67 Mad Scientist Supporter

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    Nice. I've linked your post to the Index, so if you have more information and photos, let the world know.

    :freaky
  14. mkn

    mkn Been here awhile

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    Here are the lights I bought offroadtown is the name. Remember I have a full charging system on my bike I don't know if these will work with the stock electronics on the xr400.
    I suspect your going to have to upgrade your electrics to make this work.

    Screenshot_20191009-145203.jpg
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  15. bork

    bork Been here awhile

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    When you do your adjustments, make sure engine is up to full operating temp. The mixture can also affect the off idle pickup. This video might help.
  16. Stretch67

    Stretch67 Mad Scientist Supporter

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    Not for valve adjustment though. The engine needs to be stone-dead cold for that.
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  17. bork

    bork Been here awhile

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    Stretch67 likes this.
  18. thumpism

    thumpism Between bikes

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    Here's one available locally.

    https://richmond.craigslist.org/mcy/d/richmond-1997-honda-xr400-dirtbike/6996528151.html

    1997 Honda XR400 dirtbike Street Legal - $1500 (Richmond)

    [​IMG]

    [​IMG]

    honda Xr400

    fuel: gas
    transmission: manual

    1996 Honda XR400 Dirtbike (street legal with Street title) Used, runs, has a fair amount of wear and tear. Top end recently rebuilt, Mileage unknown, speedometer not working. Has upgraded kick start shaft. Missing decompressor lever/cable, that would make it easier to start. Cold start is choke on 2 kicks, then choke off kick about 10 times starts right up. Warm start is in within 2 or 3 kicks. Sold as is, Thanks
  19. seehogs

    seehogs n00b

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    If that pilot jet is a REAL keihin then it is probably a 50 s.
    I believe the s indicates smaller side holes. Check carb passage between needle jet and idle mixture area.
    Needle jet is where main screws in. Take carb off bike to really clean
    Alcohol is for drinking not for carbs with brass parts!
  20. cmbthumper

    cmbthumper Been here awhile

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    Ramona, CA
    Slowly transforming into a SM. Made brackets to mount my Fuel bottle for Super Motor trim.


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    mkn likes this.