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Help XV250, 1995 Virago running rich

Discussion in 'Yamaha 250cc Twins' started by my67xr, Oct 29, 2016.

  1. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Hey, i'm wondering if any one has had any experience with the Virago 250's carby's?
    I am checking over and tuning my uncles' bike atm.
    The bike has done 60,000km's, and has an issue of vibration at around 2500 rpm's.

    Mixture screw was set at 3 turn's out on the BDS26, it has a foam air filter, clean and lightly oiled (factory fitted?)
    Choke is working fine
    The spark plug's aren't that old (C6HSA) but were black, and slightly wet, so i gave them a soda blast and they've come up like new.
    They have a decent blue spark when firing.

    I pulled the fuel bowl off and found a bit of dirt etc in the bottom, took the jet's and emulsion tube out and gave that a thorough clean, including blowing compressed air through all the port's in the carby.
    The jet needle and needle jet both look fine (no sign's of wear), slide move's nicely and the diaphram is all good.
    There was a bit of black stain to the engine side of the carby bore directly after the throttle butterfly which i think was caused from it running on the transition circuit and pilot jet, idle speed was turned up to compensate.
    Accellerator pump is working fine too

    I have replaced the intake manifold which was old and cracked, i had repaired it with urethane about 6 week's ago to fix a vacuum leak while waiting for the new manifold to arrive.
    New china intake wasn't the best quality, it had a rubber flap inside blocking on of the 2x port's to the head where it had been extruded or however it's made and the port's to the head were too 2mm too small as well.
    I spent about 45min's with the dremel, a carbide burr and some sanding roll's on a drum, cleaning it all up inside, getting rid of dag's and rubber and opened up the port's to 24mm as per the original one.
    New manifold bolted up to the head's nice and has sealed ok (eg no vacuum leak's)

    So i checked the fuel height on the outside of the bowl with some pvc tube connected to the drain, and it was set at about 27mm, factory spec's say 16.5mm-17.5mm.
    Fuel height is now set back down to 16.5mm.
    There is no float height setting spec's in the factory service manual.
    And no mixture screw setting spec's either (think they had a brass cap over the mixture screw as they were preset from factory), but the cap had been removed on this one.

    I've set the mixture screw to 1.5 turn's out and started the bike and let it warm up.
    The idle sound's a bit rich (slightly deep sound and putt, putt's a bit)
    I turned the mixture screw back in all the way (lightly seated) and the idle has smoothened out, it sound's close to normal now
    The vibration seem's to have gone now.


    I haven't had a chance to take it out for a ride yet, but the mixture screw been set in so far (0 turn's out) has me thinking there's still an issue.
    This carby has a fuel cut off switch as well as an electronic heater to stop it icing up in the cold
    I'm wondering if either of these could be playing up?
    I tried it with the heater disconnected and it didn't make a difference.
     
  2. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    How are the air jets and passages? They might need some threebond and compressed air. I would also try adjusting the tang on the float to shut off fuel flow to the bowls sooner. Pilot fuel screws should be roughly 3 turns out if the pilot jet size is correct. Needing them wound all the way in is a symptom of the root cause. Try one thing at a time and re-check... A pain getting the carbs on and off but it's the only way to fix it properly.
     
  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Jet's are stock 17.5 pilot, 110 main, and are all clean, done in Threebond Super Engine Conditioner for an hour, then all hole's cleaned with fishing line then blown out with compressed air.
    All air jet port's were cleaned with Threebond then compressed air, then checked i could feel it coming out the other side of the carby where the port's when through to.
    Float height was lowered to give the factory minimum fuel height, any lower and it won't be able to pick up through the main jet
     
  4. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Sounds like a mystery... are the float needle tips OK? I don't know much about the viragos, but googling BDS 26 they look the same as a 2KR carb.
     
  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah they are similar to the 2kr carb's.
    The float needle tip is soft, the seat is fine.
     
  6. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    sound suspiciously like worn emulsion tubes to be honest
     
  7. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Played with the Virago again today.
    Pulled the emulsion tube out and slide/needle
    The needle has the 2KR style retainer in the slide, a spring,plastic seat and the screw in cap, the needle sit's firm in the slide unless you push it to one side against the spring
    The emulsion tube look's round, with the the thick part of the needle sitting in it there is only a tiny bit of play there, the thick end of the needle only move's about 1mm from left to right

    I don't think there'd be much vacuum past the top of the emulsion tube at idle with the butterfly closed to be able to pull any fuel up through the top of the emulsion tube.

    [​IMG]

    [​IMG]
     
  8. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    that locator on the bottom of the needle shim has been squashed sideways, the needle will sit higher and askew with it like that.

    Long term it may have caused other issues
     
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    Last edited: Oct 30, 2016
  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Good spotting, but yeah i fixed that problem before it was reassembled.
    When i took the needle out originally the clip was sitting in the second notch from the top,
    i reckon when it was adjusted at some stage before my uncle bought it they didn't locate that pin into the hole in the bottom of the slide so the needle was sitting up too high, they then moved the needle clip up a notch on the needle to compensate.
    I've been reading any thread i can find about the Virago 250 carb's and a lot of people have been swapping the original carb's for the chinese replacement carby and that solve's their problem.

    I have just found a thread which recommend's to check the float isn't sinking, some of the bigger Virago's 700 and 1000's have a problem with the float's leaking and end up not letting the needle and seat's close which give's them a high float level and rich mixture's.
    I'll be checking the float tomorrow
     
  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Been playing with this Virago again,
    setting the fuel level is a real pain on this carby,
    the bike wont run with the fuel level set at 16mm below the slide centre line (factory spec's between 16.5mm and 17mm),
    the centre line is marked on the fuel bowl similar to the marking on the 3LN3 BDST28 Mikuni on the FZR250 fuel bowl
    The bike will run with the fuel level set at 14mm below the centre line but it run's quite rich, the best mixture screw setting is 0 turn's out.
    Any higher with the fuel level and it will run for a little while then stall out, if i remove the spark plug's when this happen's they are black

    [​IMG]

    [​IMG]



    I ended up getting a Keyster carby rebuild kit from Motorcycle Spare Warehouse for $63 plus delivery (bit rich as last week they were only $42 plus delivery !!)
    The kit come's with 2x Main jet's, #110 is the standard one and it come's with a #112.5 as well
    You also get 2x Pilot jet's a #17.5 standard and a #20 (picture show's 3 pilot jet's ?)
    It contain's the other usual part's like the fewl bowl gasket, needle valve and seat, jet needle, e clip, mixture screw/spring and washer and o ring
    You don't get the tiny rubber o'ring that goe's under the main jet, and you dont get any air jet's

    [​IMG]


    When i was reassembling it this arvo i found the needle and seat's rubber o'ring has a slot in it, i reckon it's damaged somehow at the factory?
    I will let Motorcycle spare's warehouse know and hopefully they'll send me another

    [​IMG]

    [​IMG]


    I have cleaned the carby again with Threebond Super Engine Conditioner, given it a thorough scrub and blow out.
    All port's you can feel air coming out the other end
    Hopefully this Keyster kit sort's thing's out
     
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    Last edited: Nov 16, 2016
  11. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    That is a faulty o-ring for sure.
     
  12. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I felt the split when i went to fit it, and looked closely at it

    With the price of this kit and the few part's you get in it i wonder if the FZR250 kit's will being having a price rise shortly? there's almost twice as many part's in the FZR 3LN3 etc kit's

    @GreyImport , I'm not sure i have this thread in the right section either, should it be in the Yamaha 250 Twin's ?
     
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  13. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Have you checked the valve clearances yet?
     
  14. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Nah, but i will be, why's that ?
     
  15. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Off clearances can make some engines run like they are rich.
     
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  16. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The bike was serviced and the clearance's were adjusted before my uncle bought it,
    it's done just under 1000km's since then, but i thought i'd check anyway.
     
  17. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I have spoken to MSW re the split needle/seat o'ring and they are sending me a replacement needle and seat set, and i'm sending the other one back to them so they can claim it on warranty from Keyster
    Would have been easier if they just refunded me some $ and i'd go buy a new o'ring for it.
     
  18. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    After speaking with them on the phone yesterday, and letting them know i was sending back the needle and the seat and the clear silicon cover they came in, i received the new seat today with a good o'ring, but no needle !?!? [​IMG]
     

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