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Loss of power GPX250

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Tilduke, Dec 14, 2006.

  1. Ok well I have two problems with my GPX250R 2004 model. I am not sure they are related but I would assume so as they happen one after another.

    After about 20kms of riding there is a sudden loss of power and I have to pull over and sometimes I can get it back reving again and other times it just carks it.
    It has always happened when the fuel tap is in the on position. The one time I did manage to get it back reving again was when as soon as I sensed loss of power I flipped it straight to the reserve position. I am not sure if this was circumstantial or what but I felt it was worth mentioning.

    2. After one of these stalling incidents the starter will turn over but the engine itself doesn't sound like it is firing or whatever it is called... but when I roll her down hill and chuck it into first it starts up fine and then runs fine... I must mention that I always eventually switch the fuel tap to the reserve position....

    So I am thinking that the main fuel line just isn't working and the reserve line is ... so when I try to fire it up again the carby and stuff are just empty so it has nothing to ignite ????
    I don't know I am not very technically minded here but any ideas would be much appreaciated... If there are no ideas here I guess my only option is to take it to a mechanic .. if I can make it that far... ;)

  2. I assume it's not just low on fuel when this happens?
  3. It must be the season for it. There are two threads running around here at the moment that deal with it.

    It's the vacuum line to the tank or the tank vent.

    Make sure the line is in good condition and is fitted well and make sure your tank vent is clear.
    The dealer said I had $500 free fuel, I couldn't have used all that by now...

    Seriously, nah this is on a pretty much full tank...

    Yeah I did see those threads. They seemed to have similarish problems but not exactly the same.
    So the vacuum tube you say ? I'll look into it....
    Does that explain the second problem ?
  5. Possibly. I'm guessing you run the bowls completly dry. The vaccum to the tap on cranking it over is not enough to open the tap and the bowls don't fill up.

    I'm guessing the GPX tap doesn't need vacuum on reserve, thus thats why it works when you turn the tap to reserve. The bowls fill up again and away you go.

    The blocked tank vent will present pretty much the same. It stops the fuel flowing, drains the bowls and it's not untill you put it to reserve of "pri" on other bikes, that it gets enough fuel to fire again.

    the tank vent is my best guess of the two. Pop the cap next time it happens and listen for a woosh of air.
  6. Ok so I just realised your theory might not be correct. It isn't 20kms straight .. it's just every 20ish kms sometimes with day gaps in the middle of it....it happens on the way to work but not on the way home..... (Because that is all I use my bike for)
    I opened up the tank before I left and about 1.5kms down the road it did it...

    So any updated suggestions ?
  7. So that leaves the vacuum to the tap.

    It could be the line itself is leaking, it's not fitting on one of the spigots properly or it could be within the tap itself.

    the tap has a couple of gaskets, a plunger and a spring. any of those could be not good.

    so check the vacuum line first. replace it anyway. A couple of dollars at repco.

    If it's still no good, then remove the tap and have a look. You will probably be able to buy a rebuild kit for it.

    Hopefuly it's just the line.
  8. i have 2000 model gpx250 and the fuel does not flow fuel in res and on without vacuum.

    check the vacuum line should be two one goes from cylinder two to choke and the other goes from cylinder 1 to fuel tap.
  9. So it sounds like the tap is cactus
  10. Ok so I made sure the vacuum tubes where sitting correctly and not kinked and stuff and yesterday I rode about 40 kms without it stopping so I am hoping it is sorted out.
    Thanks for your help...
  11. check the airfilter too.
    doens't really explain why it doesn't happen on reserve, but check it anyway.
    no air getting to carby means no fuel being pulled into it either, which means spluttering, and stuff like that
  12. i love this thread coz the same f'n thing was happening to me on my ZZR!!!
  13. KDE i have a 91 GPX if u want to swap bikes for a short ride. yell out. easier to diagnose after personal experience.

    hope u can work it out!