The XR400 Thread

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

  1. cmbthumper

    cmbthumper Long timer Supporter

    Joined:
    Sep 29, 2018
    Oddometer:
    1,481
    Location:
    Ramona, CA
    Awesome stuff Patagonia. That's a big elevation change for a stock carby. I live at 1452 and ride to 6200's and the reason i went to a pumper. The stock carb was way too fat past 4500ft. Runs and a beach to start at that elevation but not so good overall.
    The Patagonia Kid likes this.
  2. The Patagonia Kid

    The Patagonia Kid gnarly adventurer

    Joined:
    Feb 6, 2007
    Oddometer:
    1,126
    Location:
    SOUTHERN CALIFORNIA, Thousand Oaks.
    Have known the previous owner and bike for a long time I purchased it because I have seen it run by my side some years ago, at the time I was on my XR250R . Last ride we made together was in Kennedy Meadows ...
    The XR400R was a bit difficult to start and I personally helped the rider to get back on it / start it more than once, at the time the carb / bike did not have the mods that I performed just now and I am really curious to see if there is a difference.
    Today I went to the garage to play with it a bit and I was pleased with the way was running, but when altitude and temperature changes, that will be the real test.
    I have seen the Mikunis running and I understand some people prefer them; for now I will try the beast with this set up and see how it goes! :-)
    Good looking XR you have in there!
    NSFW likes this.
  3. The Patagonia Kid

    The Patagonia Kid gnarly adventurer

    Joined:
    Feb 6, 2007
    Oddometer:
    1,126
    Location:
    SOUTHERN CALIFORNIA, Thousand Oaks.
    Hey there, thanks for creating that XR400Index ... :-)
    I really appreciate all the knowledge we share in this site.
    shinyribs and Stretch67 like this.
  4. Stretch67

    Stretch67 Mad Scientist Supporter

    Joined:
    Mar 22, 2006
    Oddometer:
    26,503
    Location:
    Bent, But Not Broken
    Thanks. Happy to help. :freaky
    The Patagonia Kid likes this.
  5. NSFW

    NSFW who else would love noobs? Super Supporter

    Joined:
    Feb 20, 2007
    Oddometer:
    27,169
    Location:
    Burbank CA
    glad you like the RR. thanks for the link but where is it located?

    not aware of the resistor, what happens if i leave it alone?

    tia.
  6. NSFW

    NSFW who else would love noobs? Super Supporter

    Joined:
    Feb 20, 2007
    Oddometer:
    27,169
    Location:
    Burbank CA
    index is on your sigline....:clap


    Found this:

    The resistor is an RFI (radio frequency interference) resistor. It is placed in the cap to modify the RF given off by the ignition system so that it is out of the range of commercial radio frequencies. Failure of the resistor is uncommon, but I have seen two instances of resistor failure resulting in a no spark condition. You can replace the resistor and spring with a length of metal rod, copper, brass or steel. Make sure that the rod length is sufficient so that the rod is held tightly in place by the retaining screw, you don't want arcing inside the cap. I have done this mod quite a number of times on my bikes and friends' bikes. I have not found it to be an improvement in starting, idling, or engine performance.
    Stretch67 likes this.
  7. bork

    bork Been here awhile

    Joined:
    Oct 30, 2013
    Oddometer:
    796
    I always thought it weird also about the RF interference and joked with a mechanic about my radio having static. (just joking) & he said, it is to keep RF from messing with the CDI ? ?? IDK ??? plausible?
  8. shinyribs

    shinyribs Thumpers for life

    Joined:
    Sep 24, 2011
    Oddometer:
    6,850
    Location:
    The South
    I hear about elevation changes affecting carbs, but I've never experienced this myself. I live at about 1500' and ride up to 3500-4000, so nothing nearly as drastic as you experience. What exactly happens when you get "too high" with a bike?

    I'm not trying argue that it doesn't actually happen, I've just never seen it and it sounds bizarre to me. Honest curiosity.
    The Patagonia Kid likes this.
  9. saltyD

    saltyD Been here awhile

    Joined:
    May 17, 2020
    Oddometer:
    889
    Location:
    Great Southern Land
    less O2 - gets richer with altitude.
    The Patagonia Kid likes this.
  10. bork

    bork Been here awhile

    Joined:
    Oct 30, 2013
    Oddometer:
    796
    My dad bought a 1971Honda SL100 around 1973 when we lived in S. FL & hauled it up to N Ga. (approx 900 Ft alt) Went on a overnight trip with a bunch of guys up through Tenn somewhere, & high enough (IIRC 5-6000ft) where the bike would not run, it would sputter and had no power/torque and had to be towed, till we got a little lower in elevation. This is back when we could ride our dirt bikes on the streets and the law just waved. Man those were the days! Now days, if you ride the power-lines, you'd probably get arrested.
  11. The Patagonia Kid

    The Patagonia Kid gnarly adventurer

    Joined:
    Feb 6, 2007
    Oddometer:
    1,126
    Location:
    SOUTHERN CALIFORNIA, Thousand Oaks.
    Today took the time to remove the swing arm axle / bolt ... I am a lucky son of a gun! came out without major effort and looked pretty good. Cleaned a bit, greased + oiled and back to original position!

    Long live the XR400R! :-)
    and the pilot too!
    XR400R 11.jpg XR400R 12.jpg
    shinyribs, gammel, tuscan and 4 others like this.
  12. T-34

    T-34 Long timer Supporter

    Joined:
    Dec 21, 2019
    Oddometer:
    1,351
    Location:
    Jellotown, East Asia
    Guano11 likes this.
  13. schrunken

    schrunken n00b

    Joined:
    May 9, 2021
    Oddometer:
    1
    Location:
    Sweden
    Just got my ”new” bike a couple of weeks ago, got it pretty cheap cause it didn’t start and had not been used the last ten years. Now I’ve teared it apart an gave it a good service. Carburetor was clogged, fork leaking, old dirt stuck almost everywhere etc. Here in Sweden they’re not so common and this one is also street legal which is even more uncommon, most dirt bikes are run on closed tracks. I’m soon taking it out for some enduro tracks, I’m used to a 350 exc-f so it will be a big surprise. I guess the suspension and lack of e-start will be the greatest drawbacks.

    Attached Files:

    Stretch67, shinyribs, tuscan and 5 others like this.
  14. Undercover Poe

    Undercover Poe Been here awhile

    Joined:
    Sep 26, 2013
    Oddometer:
    825
    Location:
    Southern New England
    Can someone on this thread tell me. What does the current market indicate for the value of these xr4 bikes?
    schrunken likes this.
  15. cmbthumper

    cmbthumper Long timer Supporter

    Joined:
    Sep 29, 2018
    Oddometer:
    1,481
    Location:
    Ramona, CA
    That is a VERY open question in my opinion. $2500-5000

    An identical twin In CA vs say Kentucky is a $1500 difference. Throw a license plate on it and can add another $1k.
    shinyribs likes this.
  16. Stretch67

    Stretch67 Mad Scientist Supporter

    Joined:
    Mar 22, 2006
    Oddometer:
    26,503
    Location:
    Bent, But Not Broken
    The XR400 Ride Reports thread is floating around somewhere in 'Thumpers'. Give it a bump, and it'll float to the top, like cream. :lol3

    Removing the spark plug cap resistor probably won't make a difference unless one's ignition system is marginal. With a twenty-something year-old thumper with kick-start, sometimes every little bit helps. :D

    I replaced mine and its spring with a piece of brass welding rod, just to eliminate a possible (albeit unlikely) point of failure.
    NSFW and Cabrito like this.
  17. Guano11

    Guano11 Stop me if you've heard this one....

    Joined:
    Mar 26, 2007
    Oddometer:
    2,083
    Location:
    Pacific NW
    Nope. And there's no "Blue Book" either.
    For bikes this old, used is so many different ways by so many different owners, it's all about condition.
  18. Undercover Poe

    Undercover Poe Been here awhile

    Joined:
    Sep 26, 2013
    Oddometer:
    825
    Location:
    Southern New England
    It’s plated and titled. I’m going to let it go for 2500-2700. I just want to make sure I’m giving buyer a good deal and not taking advantage of him. As he is good friend.
    dlock5, shinyribs and cmbthumper like this.
  19. NSFW

    NSFW who else would love noobs? Super Supporter

    Joined:
    Feb 20, 2007
    Oddometer:
    27,169
    Location:
    Burbank CA
    looks like my memory just left me....:imaposer

    i bought stock throttle cables, push and pull, as spares.

    P/N 17910-KCY-670
    P/N 17920-KCY-671

    then this morning i realized my carb (mikuni pumper TM36) is an aftermarket....:baldy

    looks like they may work??? to confirm this, prefer not to take the cables off the bike and compare, hopefully, someone been in my situation before and can shed some light.

    :devildog
  20. shinyribs

    shinyribs Thumpers for life

    Joined:
    Sep 24, 2011
    Oddometer:
    6,850
    Location:
    The South
    I'm 95% sure stock cables won't work with the Mikuni. I say that because I've got a spare set of stock cables hanging on the wall here from being in the same situation. It's been a couple years ago, so I'm afraid to say for certain