The XR400 Thread

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

  1. JMo (& piglet)

    JMo (& piglet) Unicorn breeder

    Joined:
    Apr 1, 2007
    Oddometer:
    8,468
    Location:
    California
    Hi MartiniUp - California is actually impossible (read back a few pages if you want the full story), but most other states will want a full compliment of lights if you're converting an OHV to street bike/title (including Nevada where I was getting mine inspected), hence me covering all bases including twin mirrors - just incase they wanted to find any reason to say no...

    Jx
  2. JMo (& piglet)

    JMo (& piglet) Unicorn breeder

    Joined:
    Apr 1, 2007
    Oddometer:
    8,468
    Location:
    California
    Regarding pattern/copy engine internal parts, personally I wouldn't take the risk... the original XR400 engine is rock solid - I had over 48,000 miles on mine before it needed new valve stem seals, plus I put in a new piston and liner (and I'm still on the OEM cam which I did change at 20,000 miles, then realised I probably didn't need to do!) - and I've no double those OEM parts will be good for another 48,000 miles now too.

    If any of those high-heat/high rotational speed parts did fail, you'd pretty much screw your engine, or at the very least need a total strip-down to rebuild it...

    That is not to be disparaging to Chinese manufacture you understand, only for engine internal parts - personally I would suck up the cost of OEM for peace of mind.

    Jenny x
    bork and Stretch67 like this.
  3. lookatdirt

    lookatdirt Been here awhile

    Joined:
    Jun 1, 2009
    Oddometer:
    534
    Location:
    Arizona desert
    IMG_1150.JPG Just picked up an '01 yesterday. This will be my second time owning an XR400. I sold my old one about 10 years ago and have always missed it.
    Anyway, I've been out of the dirt bike world for quite a while and have a stupid noob question. I'm riding in rocky, sandy conditions, Arizona desert, with lots of prickly stuff, too. Some street as well.

    What should my tire pressures be?


    I'm slogging my way through this thread slowly but surely! Tried a search to no avail.
  4. JMo (& piglet)

    JMo (& piglet) Unicorn breeder

    Joined:
    Apr 1, 2007
    Oddometer:
    8,468
    Location:
    California
    You pressures are going to depend on the type of tyre you're running (brand/carcass compound and tread pattern), but I tend to run around 20psi for mixed conditions (off-road and paved sections between), and dropping to 15psi for more rough terrain...

    Actually I lie, for a long time now I've used [Desert spec] BIB mousses in my tyres (Michelin Deserts) on my XR - which are a nominal 18psi, although they go a bit softer with age and use. Best thing of course, no chance of a puncture.

    I wouldn't worry too much, just be wary that lower pressures while offering better traction in certain conditions, also make tubed tyres more susceptible to pinch flats and the tyre moving on the rim unless you're using rim-locks.

    Hope that helps...

    Jenny x
  5. mkn

    mkn Been here awhile

    Joined:
    Feb 26, 2012
    Oddometer:
    228
    Location:
    Colorado
    Very cool I have a similar story but have stayed in the dirt bike world the entire time since my last xr400 which was 18 years ago I have come full circle I suppose.

    My last dirt bike was a 2008 crf450x had a crf450r and many others before that I decided on buying a xr400 for the second time and don't regret it a bit.

    BTW I bought a set of those KKE wheels for mine the CNC set and have had them on some nasty shit and they are holding up great. 2 days ago I did a ride up Red elephant trial it's a advance 4x4 trail in Empire Colorado YouTube it it's steep narrow Rocky as hell and loose video doesn't do it justice it's so damn steep going back down I could not stop using both front and back brakes without sliding Almost the entire way down.

    The rims took some big hits with pressures at 10 psi going up and down and no damage so far and I was doing 20 plus through some knarly boulder gardens you know the saying "When in doubt throttle out" this was the saying of the day.

    A little disclaimer however... I added electric start to mine this time around. 1808650821.jpg
  6. lookatdirt

    lookatdirt Been here awhile

    Joined:
    Jun 1, 2009
    Oddometer:
    534
    Location:
    Arizona desert
    Thanks, Jmo. You seem to be a pretty good source of information around here.

    I'm assuming +/- for front AND rear?

    I see BIB mousses in my future.
  7. lookatdirt

    lookatdirt Been here awhile

    Joined:
    Jun 1, 2009
    Oddometer:
    534
    Location:
    Arizona desert

    I'm definitely into the magic button mod! Where do I look for that ?

    My last dirt bike was a 04 CRFX 250. It actually was a pretty good bike once I opened it up and re-jetted it. I sold that in about '09 (I guess that means I sold my XR about 13 years ago!) and bought, of all things, a Harley. Had fun with that and rode around much of the country with a friend. Cell phones have ended my street riding days. Its just too sketchy now.

    The previous owner of this XR had it sorted out pretty good. Its pretty sano.

    Stoked about the bike and will have lots more questions!
  8. JMo (& piglet)

    JMo (& piglet) Unicorn breeder

    Joined:
    Apr 1, 2007
    Oddometer:
    8,468
    Location:
    California
    Hi Lookatdirt - yes, pretty much front and rear, although generally speaking if you're going to change pressures, it's better to keep a little more air in the front (to help prevent pinch-flats from impacts on square-edged rocks etc.), and air down the rear for better traction.

    Mousses are certainly the way to go though - fit and forget... my currently ones have been in there for two years now (including having done the Baja Rally in 2016), the front is pretty soft now, but for trail conditions, they still work fine.

    Jenny x
    PHX_Joe likes this.
  9. PHX_Joe

    PHX_Joe Adventurer Supporter

    Joined:
    Oct 11, 2016
    Oddometer:
    84
    I ride 15 - 20, maxxis front and rear - no problems of any kind around Phoenix on 7 springs, bloody basin end to end, etc but do get some bounce on baby heads and ledges at 20. I'm no rocket, and new to xr4, jmo is an experienced desert racer, so she's the knowledge source here. I don't have the budget for mousse.

    Great bike for AZ...
  10. mkn

    mkn Been here awhile

    Joined:
    Feb 26, 2012
    Oddometer:
    228
    Location:
    Colorado
    I can help answer any questions you have regarding the e-start conversion just pm me.
  11. Stretch67

    Stretch67 Mad Scientist Supporter

    Joined:
    Mar 22, 2006
    Oddometer:
    20,280
    Location:
    Bent, But Not Broken
    gammel likes this.
  12. lookatdirt

    lookatdirt Been here awhile

    Joined:
    Jun 1, 2009
    Oddometer:
    534
    Location:
    Arizona desert
    Thanks, mkn, that is a generous offer. Let's help out Stretch, too!

    Is there a section in this 676 pages of thread that details this?

    I'm guessing that the assembly is coming off of some Honda quad with a similar engine.

    I guess I'll start my questions with-

    1. Are the parts readily available?
    2. How big of a project is it? Lots of fabrication involved?
    3. It must require a standard battery- where does it go?

    To start.
  13. Stretch67

    Stretch67 Mad Scientist Supporter

    Joined:
    Mar 22, 2006
    Oddometer:
    20,280
    Location:
    Bent, But Not Broken
    Many thanks, but what I meant was to post the info for others interested in e-start conversions. I've already built mine. :D
    Scroll down to 'Electric Start Conversions'.
    https://advrider.com/f/threads/xr400-thread-index.852074/

    ---

    There seem to be two schools of Electric-Start Conversions for XR400's.

    One is that you put the TRX400EX crank, flywheel, stator, and starter assembly in XR400 cases so that the engine will drop right into the stock XR400 frame.

    The other school is converting the bike to fit a TRX400EX engine. This is what I did.

    ---

    Posted on a TRX400EX forum after I built my e-start XR4, when someone posted that the two engines are interchangeable...



    The cases of the two engines are not identical. They will not simply interchange between vehicles.

    I just got done putting a 2000 TRX400EX engine in my street-legal 2002 XR400R. The swingarm bolt hole in the rear of the engine cases seem to differ by a few millimeters. Since that's the engine mount that can't be changed, the other mounts (except for the bolt-on front mount) must be modified.

    With the TRX engine in the XR frame and the swingarm bolt in place, the front (bolt-in aluminum) mount will mate up to the engine like it's supposed to, but the lower (welded-in steel mount) is a couple millimeters low and to the rear.

    Also, the upper (bolt-in aluminum) mount at the cam cover is about a half-inch to the rear. No problem really, just mock up new ones out of cardboard, lay out the design on 1/4-inch aluminum, then drill the holes and cut the mounts out with a bandsaw.

    The welded-in steel mounts at the bottom of the frame must be removed (cut the welds with a cut-off wheel in a die grinder) and re-welded in their new place with the mounts bolted to the engine.

    The end result is the engine being tilted forward about a half-inch, due to the slight difference between the TRX case and the XR case. One must therefore also re-locate the welded steel front muffler mount on the XR's subframe, and modify the airbox boot to come forward that half-inch to hook up with the carb's new location.




    Engine internals are mostly identical, with the exception of the crank (TRX is longer to make room for the starter clutch & gear under the flywheel), cam profile (more low-end torque for the ATV), clutch (heavier duty for the ATV).

    First gear is almost the same, but then the TRX has progressively lower gears compared to the XR...

    XR400R
    2.830, 2.620, 1.840, 1.400, 1.120, 0.930

    TRX400EX
    2.826, 2.916, 1.937, 1.473, 1.181, 1.000


    The countershaft is a bit different, in that the non-sprocket end that you see under the clutch basket is a bit bigger than the XR's. That keeps one from installing the kickstarter idler gear from an XR4. I think I can get around that by machining a different bushing. Then simply install my XR right case cover and kick-starter.

    A 2005+ engine with reverse would be nice, but those engines are about 500 dollars more than a 1999-2004, and I've spent a ton of money on this project already.

    I used a TRX400EX wiring harness, CDI, Regulator / Rectifier, and ignition to eliminate mating troubles between the engine and bike. That wasn't a drop-in affair either... scads of cutting and splicing (solder, then heat-shrink tubing) to avoid thick wads of extra wire in some spots and too short of length in others.

    Battery and box is from a DRZ400, with welded-in mounts on the left side of the subframe (opposite side of the muffler). It starts and runs great, with 14.5 Volts DC at idle.

    At times like these, Honda's lack of modularity between seemingly similar engines can be quite maddening. It has been a lot of work over the past few weeks, but I love to tinker, and I now have one damned nice XR400.

    ---


    That was nearly six years ago, and I'm still running the same setup. It was well worth the effort.

    :freaky
    G600 and Yeti2ride like this.
  14. mkn

    mkn Been here awhile

    Joined:
    Feb 26, 2012
    Oddometer:
    228
    Location:
    Colorado
    I took a picture of pretty much everything minus the crankshaft to get you started buying the stuff needed this is the bulk of what you need but minus the crankshaft. Additionally you will need a 400ex shifter the 400ex stator and a bolt Honda calls a special stud it's on the left side engine cover it's the bolt that has the 10mm nut on it.

    The xr4 bolt is not long enough to make it through the wider left engine case to screw on the 10mm bolt so you need to get longer special stud for the 400ex.

    As far as the starter you don't need to tap anything to mount it up you can simply use the existing threaded hole used to route the carb vet hoses and longer screw and use just one of the 2 mounting holes on the starter it will hold the starter just fine just thread lock the bolt. I did tap and add another screw but didn't need to.

    One thing I should point out go with a 2003 or older 400ex wire harness the wire loom is smaller because there is no reverse. I did a 07 and should have done a older one. I also used a 400ex balance shaft which you don't have to if you don't want to side by side they are different so keep that in mind. The 400ex balance shaft felt heavier as well. While your in there go ahead and through on a crf450x timing chain 112 links it's cheaper and the chain is beefier than the stock XR chain and it meshes perfectly with the gears.

    I took a picture of the battery box without welding. All I used were some clamps, bolts and nuts and sanded off the back of the drz box so it fit flush against the frame once you buy the box and look at the back you will see what I mean. With the clamps however the box is slightly tweeked inward so you need to make sure you have clearance at full bottom of the rear wheel. I did end up welding brackets later just showing you don't need a welder to mount up the battery box and can make it work.

    I also welded up some support brackets for the rear subframe I have no idea if they will be effective or not so far so good.

    I didn't go as cheap as I could go I ended up at just under 700 bucks to convert it you can do it for cheaper for sure going the plug in play is the easiest but most expensive. Standard cost to convert pretty much any current mx bike to e start is around 650 bucks for parts minus the labor BTW so the xr400 isn't far off the mark.

    Imo if you can't do the work yourself this mod may not worth doing unless you got the bike for 500.00 or less. Still a awesome mod shame on you Honda for not giving us e-start on the xr400.

    One last thing get yourself a OEM manual it's better than the cheaper manual. The Mikuni pumper tm 36 fits fine with the starter. 2098879097.jpg 685856063.jpg 1149111363.jpg 1402299521.jpg 860937828.jpg Image.jpg Image%20(1).jpg
    View attachment 1927531
    shinyribs, Yeti2ride, tuscan and 2 others like this.
  15. EnduroRdr

    EnduroRdr Woods Racer & D/S Rider

    Joined:
    Feb 15, 2008
    Oddometer:
    2,663
    Location:
    Formerly BR-LA, LR-AR, Houston-Tx, now South MS
    I used an eBay 440 bore kit that included piston, rings & cylinder.
    This in 2008 at that time was $349
    Bought gasket kit separate eBay purchase.
    Still running same bore kit probably 15k Miles on it. I forget brand name - something that starts with N. But I’m sure it was from China.

    Did my estart conversation at same time.
    I went route of installing TRX crank in XR4 cases. So I have XR top end cam etc. (no hole relocation and I retained kick start capability) - although I haven’t kick started my xr4 since converting. Estart worth every cent and hour spent doing conversion!

    I used TRX cdi, regulator/rectifier. Starter solenoid and TRX wiring harness from (2002 I think) bought on eBay. (I purchased a TRX bottom end from eBay that way I got all the left side stator stuff along with the crank).
    I think if you buy all this 1 item at a time it will nickel/dime you. I recommend buying a whole bottom end from TRX. And try to find the entire wiring harness (main with regulator and handle bar controls section) together.
    That way you get all the connectors for a nice stock Honda parts conversion.

    Regarding battery: I tried the “in the air box mount” at first - don’t do that!
    Waste of time and Royal PITA to remove battery just to clean filter!

    So I welded up a battery mount under left side number plate. I used 3/4” round stock & 16g steel sheetmetal (I have a tubing bender and sheet metal brake) Works great and solid as a rock.

    In the end all the estart stuff (battery, starter, starter gears, etc) probably adds around 20lbs - again worth every ounce! No more kicking on an off camber hill, at 60 years old I hate kicking!

    The plated xr4 is still my go to bike for single track or most DS rides.

    IMG_2468.JPG IMG_2467.JPG
  16. singleortriple

    singleortriple n00b

    Joined:
    Jul 8, 2018
    Oddometer:
    2
    Location:
    Aspen
    ** Apologies if this request is in the wrong place - let me know and I will move. **

    I picked up two XR400s last summer - a 99 that was in pretty decent shape, and a 2003 that was in slightly less good shape. My son and I rode all last summer with no problems, and most of this summer. But now the 03 has a pronounced ticking sound that seems to come from the top end. I am a noob when it comes to thumpers, and not really mechanically inclined, so could use some help.

    A couple of weeks ago, my son and I rode perhaps 600 or 700 miles (riding to Ouray, then a couple sections of the COBDR to Buena Vista) around 200 of which was on pavement. The bike was working hard to stay at 60mph-ish (bike in question has a 48 rear sprocket so rpms were high). I just checked the valves (following a youtube vid, and other than not being sure that I was at TDC on the right stroke, the process was easy) and the clearances were within spec.

    There is no decomp lever/cable, but the guide and mechanism is in place on the outside of the engine case. I didn't remove it and didn't know to ask about such. The shop I bought from (local KTM shop, the bike was owner's brother's) said the bike had been sitting for 10 years and that they had replaced the piston. I didn't ask for nor was offered details on that work. It started up and ran fine.

    Again, we rode all last summer and up til now, no issues other than a bit hard to start. This is my first kick start bike, and I don't know if it applies here, but sometimes I would get two or three kicks and then on the next kick the kickstart lever wouldn't move at all - like something was bound/stuck. Slowly pushing the lever down would get it past the strong resistance and then I could kick normally.

    I took an audio recording of both bikes on a cold start and uploaded it to youtube. The 99 sounds SO much quieter...



    Anyone care to take a quick listen and give me some hints as to what to look at next? Thanks!
  17. shinyribs

    shinyribs Thumpers for life

    Joined:
    Sep 24, 2011
    Oddometer:
    4,444
    Location:
    The South
    It sounds like the auto decomp mechanism ( inside the valve cover, attached to the camshaft) is going bad, which is not rare on these bikes. I say that since you mention the symptom of occasionally seeing a lot of compression/ bound kicker at times. Another symptom is the bike will occasionally stall/hiccup for no reason- that's the auto decomp activating when it shouldn't. I don't know if parts are available to repair it. I believe it's just a spring that gets weak causing the malfunction. When my acted up I just eliminated and rely on the manual decomp now. I find it much easier to start the bike since I could never seem to find TDC with the auto decomp installed.

    Hard to tell by sound alone. A failing auto decomp pretty much sounds just like a severely loose rocker, since the auto decomp operates by activating and exhaust rocker.

    If you are confident that your valve lash is correct, I would investigate the auto decomp or check out your cam chain tensioner, just to be sure.
    Stretch67 likes this.
  18. singleortriple

    singleortriple n00b

    Joined:
    Jul 8, 2018
    Oddometer:
    2
    Location:
    Aspen
    Shinyribs, thanks for the input!
  19. KrAzyOSUcOwBoY

    KrAzyOSUcOwBoY kRaZy

    Joined:
    Mar 29, 2006
    Oddometer:
    166
    Location:
    SW Okla
    Right exhaust valve is loose. Prob .020" and makes a lot of noise. You we likely 180* out when you did that one. Could be the decompressor, but my bet is a loose valve. .004 & .006" cold.
  20. lookatdirt

    lookatdirt Been here awhile

    Joined:
    Jun 1, 2009
    Oddometer:
    534
    Location:
    Arizona desert

    Ok. I change my own tires, adjust my valves, etc., but that's way beyond my comfort zone.

    You are a Zen Master.