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NX250 Thread -- official ADV owners manual

Discussion in 'Thumpers' started by valvecrusher, Mar 17, 2008.

  1. mattmacklind

    mattmacklind Adventurer

    Joined:
    Jul 4, 2019
    Oddometer:
    16
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    Kansas City, MO
    Took the first long ride since I acquired the bike-finally broke 100 miles total. I had the issue with stumbling but once I burned the tank down it went away so my guess is it was some old gas. Still planning to replace the plug and rebuild the carb but it can wait. Also running the Duro on the rear, so far so good.

    Attached Files:

    Spurlock likes this.
  2. Reverand Hope

    Reverand Hope Been here awhile

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    Oct 8, 2016
    Oddometer:
    103
    thanks for the shout! I managed to get in touch over on the NX250.de forum. Very helpful gent! Now searching for another unicorn...a KTM 620 cush hub that hasn't been snaffled up by EXC or DRZ owners
  3. arescec

    arescec Been here awhile

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    I am coming back from a 2500 mile trip and noticed that when the bike warms up real good (say 20 minutes on open road) it starts stumbling at high throttle (say past 60 or 70 percent). It is consistent and quite high frequency (say every few combustion cycles). Could it be too large main jet (145) or something wrong with the carb? If I back off the throttle just a tiny bit it is working fine again. The main tipoff was the fact that it is way more intense at 4000 feet plus but still the jet is not that larger from stock (142) and it has open exhaust.

    Also, are there any plug and play forks available. I saw an old XR250R and it seemed like the forks are the same, just a bit longer.
  4. Reverand Hope

    Reverand Hope Been here awhile

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    once the engine's up to temp, consistent stumbling at higher revs that goes when you back off the throttle would normally suggest a slight fuel starvation issue (eg. a dirty fuel filter, crimped fuel line etc.) but it could also indicate a number of other things. If you say it was worse at higher altitude it suggests that it was going slightly lean, so if anything, the jet would be undersized or restricted (dirty). If it was too large, at lower altitudes, it'd tend to run a bit lumpy especially on the transition from idle to main, and your tailpipe would be noticeably sooty.


    best bet is to start from first principles....remove spark plug and clean and gap it (or fit a new one) then run it up to temp. find a long quiet stretch of road, load the engine (can even keep your back brake on slightly) for a few 100m, then pull the clutch in and coast to a stop, without touching the throttle. Remove the plug and check the colour (especially the side of the electrode/insulation nearest to the exhaust side (helps to mark the plug beforehand). If it looks light brown, fuel air mixture and jetting is probably good so look for clogged filter, kinked or collapsing fuel line etc. Black and sooty would indicate over rich. Could be dirty air filter
    Light grey could indicate a manifold or exhaust leak, rather than just a carb issue....easy to check with WD40 sprayed at the manifold on idle, ie rpms increase...exhaust leaks at the cylinder head can usually be felt. It's easy to misdiagnose an air leak and over compensate by richening the mixture (ask me how I know!)

    http://www.ngksparkplugs.co.za/technical/technical-spark-plugs/

    float height is a common culprit for suspected jetting problems...always worth checking.

    Other weirdness: vapour lock on a hot day? check the fuel cap breather, fuel tank breather/return (if fitted). Does the cap hiss when you undo it? Ignition coil breaking down at higher temps but stabilizes when cooled down (had this on another bike) suppressor cap resistance increasing with higher temps (had this with the same bike)

    the good new is you can reproduce the problem, so it should be easy to trace the fault

    Fuel octane rating will affect an otherwise sorted bike set up, especially in the hills...what fuel did you put in?
  5. Spurlock

    Spurlock Long timer

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    Actually it's the other way around - at higher altitudes there is less oxygen, so the mixture becomes richer and jetting has to be adjusted leaner. Although 4,000 ft. is not usually enough to make much difference.

    -Bill
  6. valvecrusher

    valvecrusher tractus pro pensio™

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    ^^^mixture becomes richer at higher elevations..
    (less oxygen)




    Oxygen becomes richer at sea level.....mixture goes lean...



    my guess is a clogged emulsion tube inside the carb..

    it happens because of this gas they sell nowadays..

    .02
  7. arescec

    arescec Been here awhile

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    It is for sure not lean as it has larger than stock jet and stock air filter. It does not stumble when I back off throttle, but only when I either accelerate hard in 5th or 6th or try to hold the speed on uphill, i.e. twist the throttle past some 60 percent or more open.

    Echaust leak is not the issue, it got a new gasket when I rebuilt the engine and no soot around there, also checked the intake and is fine.

    Spark plug has some 6000kms on it and is iridium so should be fine.

    I use the standard 98 octane fuel but have also tried with the 100 octane today and no change.

    Carb has been rebuilt and I have been in there multiple times so I do not think it is clogged. I added a fuel filter and the last clean of the carb was when I put the larger jet a few weeks ago.

    Do not think it is the ignition coil since it is throttle and not RPM dependent.

    I will put in a smaller jet (stock) and see from there. Also have two spare CDIs so will try them too. But I think the jet is a culprit since today I have been driving next to the sea and worked almost perfectly with the stuttering being hardly noticable.

    Thanks for the input.
  8. arescec

    arescec Been here awhile

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    A few photos from the trip, tomorrow is the last day. 16 days total, around 4300km covered (2700 miles). 6 countries. Bikey did great with only the speedo failing so far (it is stuck on 0 so I cant get speeding tickets now :p).

    IMG_20190919_172611.jpg IMG_20190918_145139.jpg IMG_20190918_134000.jpg IMG_20190919_181955.jpg
  9. arescec

    arescec Been here awhile

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    Also from the trip, anybody recognizes the bike in the back on this photo? If I had a trailer I would have been tempted to just buy it on the spot. These unicorns are used as farm bikes apparently.

    IMG_20190919_095929.jpg
    jimmatas, nxcoyote and PTC like this.
  10. valvecrusher

    valvecrusher tractus pro pensio™

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    It is a

    Honda XL250 Degree (wikipedia link)
    [​IMG]

    The NX250's engine with a different chassis..
    .
    nxcoyote and PTC like this.
  11. Reverand Hope

    Reverand Hope Been here awhile

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    Think I confused myself replying to that one...! I've always been under the impression that it's less to do with the oxygen available (unless you're at seriously high altitude) and more to do with lower cylinder pressure, so the F/A burns less well....but I stand corrected.

    Glad the issue seems to have been resolved.
  12. PTC

    PTC Turd polisher

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    masshole mofo
    2D6EF264-DBBD-4F43-B530-245978F496B8.jpeg I love Vermont. Dirt roads and trails for days. Beautiful scenery, and your almost always beside a river.
    Great day up there today.
    Here’s a view from the top of okemo mountain
    suecanada, turbo3x, nxcoyote and 2 others like this.
  13. Spurlock

    Spurlock Long timer

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    Nice! Do you have a side rack to support that rear bag, or does it just hang there?

    -Bill
  14. PTC

    PTC Turd polisher

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    More a brace than a rack.
    A few brackets and a piece of aluminum plate. Bag is bolted through the plate, rock solid.
    Spurlock likes this.
  15. Kolb Driver

    Kolb Driver Been here awhile

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    Oct 21, 2016
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    Location:
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    Can anyone suggest a good rattle can primer/sealer that will absolutely not wrinkle up? Maybe an epoxy? Trying to repaint the headlight fairing and the Rustoleum metallic blue is determined to be a Wrinkleoleum. Sure wish Krylon sold a metallic blue metalflake, I never have this problem with Krylon... P1070324 (Large).jpeg
  16. kevNX

    kevNX n00b

    Joined:
    Sep 25, 2019
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    4
    Location:
    Florida
    A while back I bought my first and only motorcycle - an 89 NX250. As you can see, it was beautiful. I only had it a few months before it was stolen. TWO YEARS LATER, I open Facebook marketplace and the first post is MY BIKE! After a sting op with me as bait, I have my bike back, but it has been heavily abused. Last weekend I got on a plane, picked up a parts bike and drove ~20 hours home.

    The issues I’ve identified so far:
    The parts bike came with AX1 fairings. I either need to sell them and buy NX250 fairings or convert the headlight to the AX1 style. I’d prefer to convert the headlight but has anyone done it before?

    Next, I’m missing the fork brace that goes under the fender. Anyone got a spare?

    I just looked at the pictures the guy I got arrested posted and it looks like he took the front fender off before he sold it to me... should I unblock him and ask for it back?

    Attached Files:

  17. mattmacklind

    mattmacklind Adventurer

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    That’s very fortunate you got it back. I don’t know where you are but if the seller was charged with s crime and was arrested and bonded he likely has a bond condition not to speak to you (the victim). If you want to pursue additional items he may still have a good place to start might be the prosecutor or a victims advocate in that office. They may also reach out to you regarding restitution generally. I wouldn’t recommend reaching out to the seller but that’s just my 0.02.
  18. valvecrusher

    valvecrusher tractus pro pensio™

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    @kevNX

    Welcome kevNX! Thank you for dropping by.

    That is absolutely the worst luck, and the bittersweet ending is a kicker




    This is one of the best communities, and imho, one of the absolutely most helpful.

    If you don't immediately find a response with your missing parts,
    RE-post what you need...


    Sometimes things get lost in the hustle, but this is an awesome group, so give them a little time,
    and a chance to see ya and respond...


    (I chuckled at the unblock to get parts back line)
  19. valvecrusher

    valvecrusher tractus pro pensio™

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    Does the Rustoleum you used say,
    'Hammer(ed) Finish' Metallic Blue...

    That is itself one possible reason the Rusto- version 'wrinkled' on you...

    .
  20. Kolb Driver

    Kolb Driver Been here awhile

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    Oct 21, 2016
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    166
    Location:
    Kingsport, TN
    No, it's part # 7251 Cobalt Blue Metallic. Back when I originally painted the NX in 2016, I remember having a terrible time with it wrinkling, but that was because I was putting it on over Rustoleum Black All-In-One paint & Primer. That drove me crazy, sent various emails to the company, finally (after sanding the back fender back down for the 4th time) used a different primer - I think Krylon. Had no troubles. I'll attach a picture of how it turned out. Anyway, yesterday I sanded it down to the original Honda paint, layed 5 very light coats of the Cobalt Blue Metallic on it (40 minutes apart) and it is sitting in the shed drying, will try and clear coat it on Monday.

    Attached Files: