Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

GPX250 2000 model fuel supply problem (rather bad one)

Discussion in 'Technical and Troubleshooting Torque' started by idontlikemondays, Jun 10, 2007.

  1. this bike isnt mine!
    it belongs to my girlfriends brother, and ive offered to help him fix it up, but some guidance would be very much appreciated, since i dont know the finer technical details on carbs.

    so you start the bike up no problems, apply choke, she'll run happily at about 4 grand. however, take off, and she runs like an ant with a heavy load of shopping. seriously bad, it takes about 2 mins to get her up to 60ks, add a hill into the equation and forget it, its 20 kays. there is obvioulsy fuel starvation somewhere. at first i thought it was a blocked fast system jet. but then he told me that the problem suddenly onset after exiting a corner. the only other thing i could think of was a stuck float needle??? but yeah, we are in uni break now, so its time to fix her up. i even suggested to him to go to a wreckers and try and buy a second hand unit. would probably be cheaper than sending her in to the shop.

    btw please dont laugh at my thoughts on what was wrong! i truely was stumped when i rode it.

    but yeah any help would be greatly appreciated!!


  2. When it's in neutral with no choke, how high will it rev? All the way to redline?
  3. in neutral, about 4.5 maybe 5 grand, and take fricken ages to get there.

  4. If it wasn't for the fact you said it started to behave weird after exiting a corner, I would have started to suspect some fuel mixture problem.

    Anything blocking the airbox holes? Is the choke all the way disengaged?
  5. Well it sure sounds like carbs.
    Rip them apart, give the jets all a good clean. Check the float hights, and make sure when u put the carbs back ,they seal properly. Also that the jets are the right jets, as standard specification.
    Make sure the throttle is adjusted to specifications, and that the slides are in sync.
    Check the fuel lines, install a fuel filter cause most fuels have deposits that will block up the carbs.
  6. Does it keep running under load with wide open throttle?
    Does it miss or idle smoothly with choke on and off?

    Suspect needle/seat or float level, main jet blocked?
  7. Hmmm, I had a GPX but can't remember the exact carby configuration so my next comments could be irrelevant.

    The same issue happened on my 9R because a simple vaccuum hose had falled off. It'd start and rev fine, but under "load" piss and fart around.

    Take the tank off and have a good look around, especially any hoses from the air intake to anywhere on the carby bodies.


  8. thanks for the help guys. yeah the first thing i checked were vacuum lines, and i could only check the expoosed ones since at the time we didnt have the means to start stripping her down. they all seemed in place. i couldnt check any of the breather lines into the rocker cover, so that could be it??

    it idles fine, it fast idles fine with choke. the revs just crawl along and wont go any higher than about 5 grand. give her a hill to run up in first, and its like trying to get it up in 6th at 20ks. after doing a bit of research, i can only come up with a clogged main jet. is it possible that the fuel filter got displaced and a bit of debris has worked its way down?
  9. if the bike has a fuel filter... a lot of em don't, my GS doesn't...
  10. ZZRs got them in 02 or something like that. Also, even when they started putting them in, they were really small and didn't do a whole lot.
  11. shit so im guessing it wont have a fuel filter at all. no bloody wonder the jets might be clogged.

  12. ANy smoke? Maybe air filter got a does of oil.
    Check everything else before tearing into carbs, like ignition.
    I've fixed many fuel problems with plugs and leads...........

    Regards, Andrew.
  13. na no smoke.
    leads and plugs never even crossed my mind! will check that when im looking at it!
    thanks andrew!

  14. maybe the carbs?
  15. lol, just a bit of late follow up on this. problems were the main jets, clogged up real bad, there was a thick light browny coloured sludge in the bowls and the jets. other problem was the vacuum chambers, missing screws and loose. which ever dickhead sold it too him must have known of problems, the carbs had '02 ZZR250 written on 'em. shes obviously had fuel problems before.

    kudos to people that own kwakas, i have never in my short mechanical experiance worked on such a difficult piece of shit. you have to bascially strip the bike down to remove the carbs.
    thanks guys to all your help for this in the past for this one

  16. I told ya the main jest :wink:
  17. LOL! :LOL:

    I'll second that, the only harder things to work on are Australian built cars...