Engine Stalls At Low Revs

Discussion in 'Technical Discussions' started by Wizard, Oct 21, 2016.

  1. Hi all,just bought a 2009 Yzf R125 (2009) the one with the Rossi Moto GP Paint Job

    Bike runs great,only trouble is it tends to need reving a bit when i stop in traffic or it stalls.

    It does have an aftermarket exhaust,shop didnt know the make nd i cant see it anywhere on google,kind of a weird little bend,little bend affair like a hobbit houses chimny.Dont like it much and will prob go back to original or other..

    Bike just had new battery nd spark plug and under warranty from shop.

    Edit:So far google shows Faulty air filter?Fuel filter.maybe even faulty fuel injector...oh well its still under warrenty.

    Thoughts anyone?

    Last edited: Oct 21, 2016
  2. Blazer

    Blazer Member

    My first thought was a battery or charging problem, if the battery is low or there is a charging problem, then the engine warning light will come on at low revs and once the revs are increased the engine light will go out. As you have changed the battery it could well mean the generator isn't kicking out enough power and power is being drained from the battery, i had this problem before and after charging the battery it would last a week before it had to be recharged, until the generator finally packed in. If you still have the original black rubber spark plug cap on, then it could be that the screw that secures it to the lead could have snapped off which is a known problem, if it is an original cap then unscrew it to check. Yamaha will replace it with an aftermarket one, usually NGK.
    Hope this helps.

  3. Blazer thanks,guy at shop thinks its a filter problem so far and/or linked to the aftermarket can,so were going to stick the original one
    which came with the bike(changed by previous owner) back on,check the filters nd see if that sorts it

    Thanks for the heads up on the Gen and spark plug cap, i,ll get them checked also (my first bike for ten yrs so im rusty on maintenance)

    Great bike to ride so far part from the stall/cut out at low revs,can see why people like them..going to be using this one for every day transport for a while so its got to be set up right..ok thanks again fr the info.
    Blazer likes this.
  4. Blazer

    Blazer Member

  5. Thanks fot the link boogaloo,looks like a usefull site..bikes under warrenty fr now but gonna do as much maint myself as i can to keep up to speed nd save some of the hardly earned.

    Its a nice bike to ride,handles great when its not stalling..shop thinks the,ve sussed the problen to filters nd the aftermarket exhaust.

    Not a sensible bike really as i havnt ridden in 10 yrs,plan is to learn this one nd go to an r3 maybe or even a ninja..or even bore it out to 180 cc with a Mallosi kit..im just crazy enough to attempt that heh,heh.

    Ok thanks again,sweet runnings

  6. Ok..fuel injector replaced,original exhaust refitted,engine stripdown reveals bored out to 150 nd tuned...thought it was quick.

    First blast out and its perfect..great power delivery,good throttle response...even oncoming cars smile nd wave at me (nice looking bike i guess)..happy days:)
  7. Blazer

    Blazer Member

    Great to here you got it sorted, suprised they didn't try to say the warranty was void when they found it was bored out to 150cc. Sometimes a 150cc kit can stall at tick over when it's new, adjusting the idle screw on the throttle body usually does the job, until it's run in. Fitting an injector that has more holes is probably better though.

  8. Interesting,thanks..the 150 kit doesnt seem too well thought of but it seems really smooth when its working ..(see below) the guy at the shop is a good guy,indepenent dealer,honest and knows what hes doing,he offered to put it back to 125 if it was going to be a prob nd not charge me labour cost

    ..anoyingly ive now got starter problems so back to the shop it goes..swap it for a cbr?at least ill be able to ride it :) currently laid up with some horrible stomach bug so bike will have to wait a few days..seriously starting to wonder if ill get a reliable ride out of this monkey..time will tell..might consider the swap option if there too many more probs..shop would probably do it.

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