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GPX 250 increases revs by itself

Discussion in 'Maintenance and Servicing' started by peter1929, Mar 13, 2012.

  1. Hello All.

    The story, 6 weeks ago i got my local repair person th balance the carbs, this was done i did not notice much difference.

    I was advised of a top end noise ( yep i new of this).

    Last weekend I took the cover off and checked and adjusted some of the valves that seemed to be a little bit loose.

    While apart i noticed the cam chain was a little bit loose ( between the cams)
    I loosened the ctt about 5mm and the chain tightened so i pushed up and down a few times, seems it may have been stuck loose and not putting pressure on the chain.

    Bike now runs quiet, only problem is now when expect the revs to drop down they seem to hang between 3-4k, at a set of lights I partly engage the clutch to slow the motor down to 1.5k. all good.

    Then the revs will increase up again?

    would you say the floats are set to high causing this.

    help appreciated.
  2. Peter, I'm a little bit worried about this, because there's so much you don't mention, and some of the stuff you do say sounds like a highly competent and knowledgeable rider / home mechanic, and some sounds like you ... haven't done much of this stuff at all.

    If you're not confident in the quality or value of the work done by your local repair person, take it to another one - a shop, with qualified mechanics, and (ideally), a shop that sells new examples of the brand of bike you ride. Tell them the whole yarn and get them to look at it.

    With respect, I would suggest that if you don't know how to balance the vacuum of the carbs (not a trivial job, but not brain surgery either) then perhaps you should leave the valve covers on it. I'm trying to be really tactful about this but I think you're biting off a bit more than you can chew, and you might get a better and cheaper in-the-long-run result if you take it to a pro.
  3. Disregarding all the rest of it for a minute, have you adjusted your idle speed since the carbs were synced?

    Warm the bike up well, then set the idle where should be if you haven't. You may need a bit more choke in the mornings/cold starts, but that's pretty normal...
  4. A competent home mechanic using clutch drag to bring the revs down??

    +1 what KD said.

    - - -
    Tapatalking loud, saying somethin'
  5. Yes I have.

    still will rise up by it self , but has more power now .
  6. leaking air?

    Start it up and give a spray of "start ya bastard" around your airbox/ carbys. If it really starts to rev, you have a fouled or leaky airbox/ carb connection somewhere.
  7. Does float level effect idle speed and stability? Yes, to some extent, but it's not the primary control of that parameter.

    If you knew for certain that your mechanic, who was going to adjust your valve clearances and cam-chain slack, didn't understand idle-speed / float level adjustment... If the same bloke set your valve clearances by 'seemed a bit loose' and tried 3 different methods of setting / correcting cam-chain slack adjustment - none of which are right - and generally demonstrated a flawed / imperfect understanding of how things work and how routine maintenance jobs are performed - would you send your bike there to be serviced / fixed? Or, would you suggest very gently and politely, in terms designed not to challenge or offend, that he take the bike to somebody who actually knows one end of a screwdriver from the other?

    I am doing advanced level exercises in self control to NOT provide detailed instructions in how to go forward with this, because I think I'd like a pro to be involved at step one.
  8. haha, I totally agree!

    I have never adjusted a "loose" valve clearance, EVER!
    Back in my day we adjusted them with a set of feeler guages!

    My advise would be to take it to a (reputable) motorcycle mechanic and pay the $$ to get it sorted properly.
  9. Nothing has changed. Factory trained mechanics are still trained to use feeler gauges.