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choke/cold start problems - NEW GPX250

Discussion in 'Technical and Troubleshooting Torque' started by helent, Sep 21, 2006.

  1. Hi
    I have mentioned this before (hijacked somebody else's topic, thought I would start my own this time), but things still do not appear to be right and wanted some advice.

    Bought a brand new GPX250 a few weeks back, and since I have had it, starting it from cold has been a problem. I have the choke up full, but unless I keep the throttle up, the revs just die out and the bike conks out. I have to keep the throttle up a little for at least a couple of minutes, before I let the choke do its thing on its own. Occasionally, if I give it a really good revving, then the revs will stay up for a little while, but usually they die away again, and the bike still conks out.

    I presume that this isn't a normal GPX thing and that the choke is supposed to work on its own without all that additional throttle stuff? In fact, I borrowed a loan one when mine was being looked at, and this started up really pretty sweetly for a old bike.

    It has been back to the shop twice - the first time they couldn't find anything wrong with and sent it back to us without doing anything (I think they left it in the shop rather than the workshop, so it probably stayed nice and warm). Found it still had a problem, so back it went. This time the guy said he also had a problem starting it up, so they cleaned out the carbs and played with the fuel screw (I think) but still couldn't really find an explanation for it. Said that was all he could really do.

    But it is still happening :( What do I do now? Any thoughts?

  2. Could you explain exactly how you start the bike please?
    If you leave the choke full on, the bike will die. You have to adjust it like a throttle.

    Regards, Andrew.
  3. Is the bike new from a store?

    If that's the case, I wouldn't say that it's all they could do. It's like saying well it's a broken product too bad... you know? I mean, from the looks of it it's just like, 1 month back. If it's a problem then they need to fix it... I mean.. isn't it under warranty?

    Asides from that I'm not a techie, but as typhoon said, the choke is kinda like a throttle, you can't give it too much or it'll die, just have to adjust it just right.
  4. Well, it has been coldish, the bike is parked in a shed, so before I start it, I put the choke up full, and press start. The bike fires up. If this is all I do the bike will immediately conk out. So as soon I press the start button, I have to start giving it revs on the throttle, and keep giving it revs, or the bike dies. Like I said, I usually have to keep the throttle on for maybe two minutes before I can leave it. After throttling (gently) for a couple of minutes, the engine presumably warms sufficiently that I can let the throttle off, and the revs stay at maybe 3000 rpm. I then slowly let the choke off - very slowly or again the bike dies. maybe takes 5 minutes all up. But I am concerned that I need to keep the throttle on at all.

    I don't think it has bee getting too much choke - there is no way it would start if I didn't put the choke on. And it is not exactly summertime round here at the moment.
  5. I assume that this problem goes away once the bike is warmed up? That might indicate that your mixture is too lean (not enough fuel), even with the choke on.

    One easy thing to look at would be adjusting the pilot or air screw on the carburettors. It requires no real mechanical know how either (and made even easier with the use of a service manual).

    Locate the air/pilot screw on your carburettors (you may or may not have to take the fairing(s) off for this, service manual comes in real handy here). Using an appropriate screwdriver screw in the screw (or screws) and count the number of revolutions it takes to screw all the way in (as soon as you feel it touch don't screw anymore). Write this number down.

    Now you can play around with the setting for the pilot scew. Generally you screw it in to richen the mixture (more fuel) and unscrew it to lean it out (less fuel). Try about a 1/2 (or even a 1/4) of a revolution more screwed in than how it's normally set. Then try to start the engine (without the throttle) to see if that has improved it any.

    When your finished mucking about just screw the scew(s) in all the way again, then unscrew them the number of times you wrote down. It's back to how it was now.
  6. I had a similar starting choke/throttle problem a little while ago with mine but found that if I bought cheap discount fuel it was more likely to occur. Not technical I know, but might be worth a try.

    Otherwise nag ! Youve got warranty :grin:
  7. Cheers haggismaen (what on earth does this mean by the way - are you Scottish? what is the 'maen' bit at the end, sorry just being nosey)

    I will try your suggestions, and see what happens! Although I thought they already did this back at the shop, but I guess if you want something doing properly and all that.......
  8. And I did mean to say, yes, once it is warm, it is fine.
  9. have you tried starting the bike with a different amount of choke. sometimes you can give it too much and the same will happen. try pressing the starter button with no choke then while the engines kicking over pull the choke on when the bike starts stop pulling choke lever and leave it there

  10. The bike came with a full tank of fuel, we have just filled up for the first time last week - hasn't made any difference, and I don't think the fuel we put in was especially cheap!!!! (is there any such thing as cheap fuel these days :grin: )

    Anyway, I do agree, I should keep nagging, I am just getting fed up of taking the bloody thing back to the shop. I live a 45min drive away from the shop, and because I am on learners, I have to get my husband to take it in (good ol WA licence conditions), and he can only do that either late night opening (which means going all the way home after work - 1 hrs drive - then riding into the shop - another 45 mins - and then riding back - another 45 mins, or doing a similar thing on a Saturday morning - which stuffs my Saturday up, cos I want to go riding, the two of us can't go cos my son does not want to go on the back of our other bike all the way for 45 mins there and 45 mins back, and we have no-one to babysit. So I end up in the car, watching my husband ride MY bike. When I should be riding :(

    I mean how often do you need to take something back before they will fix it?

    Sorry rant over. :)
  11. by cheap fuel i think people mean non shell/bp/castrol fuel stations.

    also the pilot mixture screws on the gpx work well on 2 - 2 1/2 turns out. but i would imagine this would be set from the factory.

    anyway goodluck
  12. Yes, I know, just my crap sense of humour :wink:
  13. Hi Helent . Heres my start procedure on cold mornings. Choke on full , just as you , hit the start button , bike fires up and the revs hit 3.5 / 4 . Then start closing down the choke untill the revs are at 1.5. The revs then build up again but I keep using the choke to maintain close to the 1.5 . You can hear little surges/variations in the engine revs untill shortly after when all the oil and fuel and stuff has calmed to a steady state , and then I close down the choke. revs sit at 1.

    Its hard to tell from your description whether or not you are flooding it by having the choke on full and then throttling it .
  14. You tried starting it without the choke at all?
  15. I have a 92 model GPX and I just start it - no choke, no throttle. It starts straight up almost everytime. I only give it some throttle after it starts.
    The only time I used the choke at all was during the coldest days in winter...ice in the dog's bowl days.

    So yeah, I'd be thinking something's wrong with yours.
  16. bring it to a different workshop and get a second opinion... brand spanking new bike should not behave like that where bonkers' one is working fine..

  17. Two things I can think of. One is your choke cable is incorrectly adjusted- you aren;t getting full choke. And two, maybe you need to use full choke to start the bike, then immediatly start easing the choke back. If I read you correctly, you are running the bike for minutes with full choke, and using throttle to keep it running. You should only need some evry light throttle, and modulate the choke to keep it running sweetly.
    Try starting with full choke, and as soon as it sounds like it's starting to run rough, ease choke back until it runs more smoothly. You should be able to get the choke off in about 10-20 seconds max.

    Regards, Andrew.
  18. My bike has peak revs about 2/3 choke. If I go past that the revs drop off because it's just way too rich.

    so try the no choke and half choke techniques described above.

    Also what does it idle at when fully warm?
  19. Thanks for the replies. I will play with the no choke over the weekend (although hubby tells me he has already tried this). I am inclined though to think there is something wrong with it. Like I said, I had a loan gpx250 one of the times my bike was back in the workshop, and had no troubles at all with this one. It just started as it should, no problems. It is not that I am leaving the choke on too long - the bike just cuts out immediately if I do not throttle it. When it does finally start warming up and I let off the throttle, I can't ease off on the choke for another few minutes, if I do, it immediately cuts out again.

    Idling speed when warm? About 1500rpm I think or thereabouts.

    Ah well, I think my bike will be taking another trip back to the shop.......
  20. My housemates ZZR is like that... I'm putting it down to "running in" issues for the time being.

    Once it's warmed up, it goes alright.

    Keep us posted. :)