NX250 Thread -- official ADV owners manual

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

  1. fikse

    fikse All-season-rider

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    OK... Im a complete newbie to the Nixie (others here have experience in this engine, I have not), but replacing the exhaust to a supertrapp I think should force some richer fuel in all areas. You might should consider a Colortune to see whats going on, and maybe you will try a Sigma Carburettor kit :1drink

    You could also check for airleaks in carb. Spray some start-gaz on the carb while running/idling. If RPM is changing, you have some work to do ;-)
  2. SaDoW

    SaDoW Adventurer

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    Noted

    thank you!
  3. RollingJ

    RollingJ The mud in your eye

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    I hate to say it, but I will say it loudly. Fikse is dead wrong.

    An aftermarket exhaust will flow much more air than stock, and the bike will be in a serious LEAN condition until you re-jet with larger size jets and possibly shimming the needle.

    If you put an aftermarket can and haven't yet jetted richer, you take a real chance of putting a hole in your piston!
  4. jeepxj

    jeepxj n00b

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    Hey guys great thread. Got an 88 250 just did the valves put it back together and it is sputtering around 4k gets a little better when warm but still not right. Idles fine and am assuming carb issues and was wanting ideas as well as a picture showing the hoses connecting to the carb. Maybe I ran something wrong. Thanks for the help.
  5. fikse

    fikse All-season-rider

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    I dont understand what you think is wrong. Im also into the lean condition, caused by a more free flow. Thats why I recommend a jet kit (the Sigma is from stage 1 to 3, whereas I would recommend to start at No1).
    I belive we are talking about the same thing but with our own words :wings

    English is definately not my mothertongue, so please bear with me if its difficult to understand my points....

    EDIT: OK, I see it now. This one:
    OK... Im a complete newbie to the Nixie (others here have experience in this engine, I have not), but replacing the exhaust to a supertrapp I think should force some richer fuel in all areas.
    What I mean is that mixture will be LEAN (if you dont do anything), but you are forced to jet/adjust the carburettor, if you want the engine to survive... . OMFG, thats a bad sentence ;-) Sorry!
  6. scrambler66

    scrambler66 Been here awhile

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    145 main jet - thats already a lot. I guess your lean mixture is due to air-leaking of the carb, have you seen this?

  7. SaDoW

    SaDoW Adventurer

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    yes i have

    mine is with the aluminium top not the plastic

    also i have new gaskets installed


    i will try the test with a carb cleaner to see if i have a vacuum leak
  8. muddyrabbit

    muddyrabbit Lost Boy

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    Parts coming available.

    In the next couple of weeks we are going to swap the front wheel on the project NX to a 21. Since there is a usable 21" rim and spokes in the garage we are lacing that rim to the stock hub. That will leave a very good condition NX250 front 19" rim, spokes, inner tube and tire available. The tire is a Kenda Big Block, and both tire and tube are nearly new with only 1000 miles or less. Would like to sell it all together if anyone is interested, pm me.
  9. clanbree

    clanbree Adventurer

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    249cc
  10. SaDoW

    SaDoW Adventurer

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    by float level you mean the needle position

    the neddle has 5 positions

    from TOP to Bottom i am in position 3 you mean to go in position 4 and 5?
  11. clanbree

    clanbree Adventurer

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    No Sir. The needle position will enrich the mixture at part throttle operation, but do nothing for fuel mixture at or near wide open throttle settings, which is where your problem is occuring.

    Inside the actual float bowl (where the float and needle valve live) you can adjust the level at which the float shuts off the flow of fuel into the carb by bending the metal tab on the float that activates the needle valve. Much like bending the arm on the float inside the tank of a commode to increase the amount of water held in the tank, raising the float level in the bowl of the carburetor increases the volume held in the bowl making it easier to draw fuel though the jets and into the engine.
  12. jeepxj

    jeepxj n00b

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    Any help...
  13. RollingJ

    RollingJ The mud in your eye

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    Alright jeep...

    Since it was constant throttle I will rule out the a-pump for now.

    How was it running before the valves were done, and what was the condition of the valves and piston while apart? (lI doubt there was lots of carbon build up, I'm guessing it was fairly clean of black carbon and was closer to white and chalky because it was lean)

    Have you gone through the carb and checked your jetting and needle position? Shimming the needle would richen the mix at 1/3-2/3 throttle.
  14. valvecrusher

    valvecrusher tractus pro pensio™

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    working on the WyoWilly filter mod, v.2
    WW used the mg-1001 filter, using the above spec'd sizes..
    this time, the 33--2633 is going to get a shot...
    post pics when receive and work the new filter..


    trivia:(the CBR250R uses a similar filter by area as the ol' NX)


    ordered the #33-2633 Daihatsu Mira Turbo and hoping to make a 'drop in' type filter using the stock filter cage?
    found the filter for tax + shipping total..$21.81
    [​IMG]

    It should be a 'weekend project'...and hope to find a cheaper alternative to the WyWi-af-mod, or the DNA air filter.

    post it up when it resolves..




    Thanks RavenRanger...i thought i recalled this info being posted before...
    .
  15. muddyrabbit

    muddyrabbit Lost Boy

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    We were just discussing the air filter at our place. I plan to cut the paper element out leaving just the rubber outer part, and simply use that to hold ina filter cut from Uni filter foam. Will cost about $5.
  16. muddyrabbit

    muddyrabbit Lost Boy

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    Decided to get it done this morning. Here's the documentation:

    First, remove filter paper:
    [​IMG]

    Next, I scored the plastic with a razor knife, then folded it over for a nice clean break to remove the excess part:
    [​IMG]

    Which left this:
    [​IMG]
    I also used course sandpaper to remove the rest of the paper where it was glued in after this pic was taken.

    Traced out the shape on a sheet of Uni filter foam with a fine tip permanent marker:
    [​IMG]

    You can see you get plenty of foam for several filters in one sheet. Scissors work better than a razor knife for cutting the foam.

    Note that I cut it a few millimeters over sized to make sure the frame would have enough to grab onto:
    [​IMG]

    Then just line it all up and tighten the screws.
    Installed in bike:
    [​IMG]

    Now you have a cleanable filter. Took about 45 minutes including taking the pics. If you wanted to get really crazy you could order pre-filter foam, cut that to fit in the black cage and glue it in, then you would have a dual stage filter.
  17. valvecrusher

    valvecrusher tractus pro pensio™

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    That's clean, and cheap!

    To any future readers, if you choose this route, remember,
    Unifilter foam is already fuel/gas/oil resistant...and your 'general foam sheet' from the fabric store/walmart is not fuel/oil/gas compatible.

    (front page notation for you muddyrabbit, thank you!)

    it's very similar to my approach, also...
    I'm hoping the cage of the new Diahatsu filter drops into the rim of the old rubber from the original filter.

    *post reserved* for VC air filter shots
  18. valvecrusher

    valvecrusher tractus pro pensio™

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    *post reserved* for air filter fabrication
  19. muddyrabbit

    muddyrabbit Lost Boy

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    A whole sheet of that foam is only $13. I keep it around, never know when you'll need it.
  20. polarized

    polarized Dirt Virgin

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    Apr 16, 2012
    Oddometer:
    23
    Seems like a really quick and easy way to replace the stock filter.

    How rigid is this Uni foam? Just wondering how it will hold up over time with induction trying to draw it inward.

    cheers.