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Help 2008 V-Star 250 with fuel delivery problem.

Discussion in 'Yamaha 250cc Twins' started by dynaryder, Aug 9, 2018.

  1. dynaryder

    dynaryder Member

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    Hi Everyone,
    I am new here but it looks like Yamaha XV250s will be part of my life for some years to come. My daughter loves this bike and I recently picked up an older on on the cheap for use as a "guest bike" (and a learner bike, I guess, for my grandkids).

    My daughter's 2008 model has been in my possession for a while due to it having been in an accident. She did not have the accident - someone else did....anyway the DAD Guarantee Insurance Company is paying to fix it. The bike has sat since last September. I repaired and upgraded a lot of parts on this bike and I am now down to making it run properly. I was not able to start it at first but I fed gas into the float bowl vent port and I was able to start it up - and ride it - although, unless I was running it at more than an idle it seemed to want to stall. It would restart and run though. I rode it for at least a half an hour and it ran "fine" (If I am feeding the fuel into the vent port, fine is a relative term.) Suffice it to say that in my mind there was nothing wrong with the idle/low speed or the high speed circuits in the carburetor.

    Now, the problem is that when I reconnect the fuel lines correctly, even though I can get flow through both the petcock (set at PRIme) and the vacuum fuel pump, the carburetor float bowl will not seem to either fill or fuel the engine. If I leave it set on prime for an hour or so, the engine will start for about literally two seconds and then die. I tried pumping fuel into the float bowl vent port and it will start and run briefly again. I was also surprised to find that there seems to be huge restriction in the fuel inlet port on the carburetor and the orifice (which looks to be about 1/16" or 1.5mm in diameter) for the seat in the float bowl.

    The first question I have is - Is the impression of a lot of back pressure - as in at least 1/2 a psi - a normal situation?

    The picture attached show two items. The larger item is the jet holder Internally, it is clear and clean. The smaller item seems to be a jet but it is not...there is a hole up through the center but it seems to dead end just prior to where the threads end. The bore, from the opposite end goes through the extension that had the bleed holes and dead ends about 1/16" high of the dead end from the opposite side. The next question - Is this correct? 20180808_151122.jpg

    I have, of course gone into the carburetor to get these parts in order to photograph them. There actually was some fresh gasoline in there - but less than I would expect.

    I have reason to believe that this is a simple problem .... What am I missing? Is the float level too low? This I find hard to believe because the bike ran fine prior to the accident.

    Can someone offer me some insight here?
     
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  2. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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  3. TonyZXR

    TonyZXR Active Member Premium Member

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    if no fuel is going into the carbs i would be pulling the needle and seats out and check that the mesh screen isn't blocked with rubbish
     
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  4. Murdo

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

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    As above re blocked screen. Can you blow with compressed air back through the needle seat (ie in opposite direction to fuel flow)?
     
  5. dynaryder

    dynaryder Member

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    So far ....thanx for the replies.... I now have fuel delivery. I benched the carb and cleaned it out (a second time) I considered chucking the seat in the lathe and boring the hole out to about twice the area but decided to try flowing fuel in to the carb. I also wanted to double check the operation of the vacuum pump. With the float bowl removed, a gas can on an upper shelf with a dip tube and fuel line, a hand held vacuum pump with an air bleed in the actuating line and rapid pumping I was able to flow fuel as fast as I could pump through the needle and seat. The carb was in a one litre plastic food saver container in a large plastic catch tray. I pumped a half a litre of gas through the carb fairly quickly. I reassembled the carb and put it back on to the bike. I primed it and cranked the engine over...It started briefly again - for like two seconds and died....(It runs on both cylinders when it fires)...and I could get it to briefly fire several times in a row. I checked the float level according to the way I read - with a clear plastic line off the drain. The carb definitely had fuel in the float bowl and the level may be a bit high. It was getting late, so I called it a night.

    So - next question - Is this other than a fuel deliver problem now? I found that the clutch lever safety switch was damaged and playing with handlebar position caused one of the wires to break off. I pulled the switch apart and soldered the wires together. The bike now cranks over with the clutch lever either pulled or not pulled. So, upon removal of my finger from the start switch, does the power to the coils get shut off due to a malfunctioning safety switch ....and does the power reset with turning off (and then back on) the key? This damaged switch became apparent AFTER my try out ride as described in my initial post.

    Am I chasing a "will o' the wisp" here?
     
  6. dynaryder

    dynaryder Member

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    Update.... I got the bike to run again. After a good warm up, it seems that the carb is doing its job and the bike is running the way Yamaha meant it to run. I also pulled all the ignition electrical connectors apart and reconnected them as well. there was no corrosion or anything that led me to believe that an ignition problem was present. I ran the bike up to a good warm "operating temperature" and all seems to be well now.

    On the matter of the faulty clutch lever switch. It looks like it does not interrupt the circuit which is a potential safety issue to a newbie rider if they try starting the bike in gear. I do not know what we did all those years prior to safety items like this - bruised our bikes, our bodies and our egos, I guess....
     
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  7. my67xr

    my67xr Senior Member Staff Member Premium Member Contributing Member

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    I've worked on my uncle's 1995 XV250 Virago before trying to get it running right, the Virago 250 and V Star's don't like the fuel level being too high.
    The earlier Virago 250's it should be 17.5mm below the accelerator pump piston valve.

    This is a picture below is for the earlier Virago XV250, might be the same ?
    You'll hear the engine sound change when you get the mixture screw set right, they seem to sound a bit bubbly when running rich

    I also fitted a #20 pilot jet to replace the standard #17.5 pilot, it made the power delivery a lot stronger, even in the top end.
    Throttle response was much better though.


    With the clutch switch try spraying some contact cleaner inside it, and move the lever a lot, then repeat.
    Could also try WD40 or similar if that's all you have.


    20161116_165155_zpsfq9jjw5n.jpg
     

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