2010 Yzf-r125 Power Loss Please Help

Discussion in 'YZF R125 General Discussions' started by Luke Saunders, Feb 9, 2017.

  1. RPS

    RPS Member

    Early 125's circa 2009/10 did have fuel pump problems and low mileage bikes might not be afected until later in life. My 2010 wr had 2k miles on it in 3 years then i put 7k on it in 18mths before fuel pump died. Quite expensive to replace with a new one. Early forum threads discuss this issue but your bike is certainly at possible risk of developing this fault.
  2. RPS

    RPS Member


  3. The primer works, I hear it when I turn the bike on. I have removed the spark plug (brand new one) and it does indeed spark... does this mean its possibly a mechanical issue?
  4. Blazer

    Blazer Member

    Unfortunately if there is a spark then it won't be an electrical issue, and if the fuel pump primes then it is less likely to be a fuel problem, although i would take the fuel pipe off the throttle body and turn the engine over to see if any fuel shoots out, if not then it's just a matter of working your way back to the fuel tank looking for problems. If fuel does come from the pipe then there is only one thing left to check, and that is the fuel injector itself, the holes in the injector are tiny and could have easily become blocked, you will have to remove the airbox and possibly the tank to gain access to the injector. If you do decide to remove the injector, then be carefull with the black plastic spacer, it can easily be cracked. If the injector is blocked then it would certainly give the same symptoms as you described in your initial post. Once you have proved the fuel is getting to the engine, then i'm afraid it looks like it could well be a mechanical issue. One last thing you could try is get the cylinder pressure tested.
    Last edited: Feb 13, 2017

  5. Okay great, suspected it could have been injectors a while back when I had minor losses of power and the symptoms matched... Thanks for the advice blazer, it really helps. I will inspect fuel and see if it shoots out, I personally think its injectors. I'll update this post when I've checked the fuel.

    Thanks again

  6. Blazer

    Blazer Member

    Sorry!, forget what i said about removing the fuel pipe from the throttle body or removing the airbox, the fuel pipe doesn't go to the throttle body and it shouldn't be nessesary to remove the airbox to gain access to the injector. You will need to remove the tank and a few panels though.
    The injector is held in place with just the one bolt labeled 'B', The fuel pipe should just un-clip from the tank, fuel won't drain out of the tank when you remove the fuel pipe so no need to block it.
    Last edited: Feb 15, 2017

  7. Wow thanks mate! I'll get onto that tonight!

  8. Hi guys, just a side note; just cracked open the airbox, no problems with the airfilter but found this liquid at the bottom of the box... Took it out its not viscous enough to be oil... it's a funny colour and does not smell like fuel or oil... Any ideas what this is and how it got into my air box?

    Attached Files:

  9. Blazer

    Blazer Member

    It's just a little condensation, due the cold and humid winter air meeting warm air. There is a special clear cap underneath the airbox with a butterfly clip, that should be removed from time to time to drain it.

  10. Alright, time for an update.

    I've now replaced the oil filter, the air filter, i've put flushed out all old oil and replaced with brand new oil. Battery is still fine, spark plugs do spark, bike will turn over, but still, it will not start. I've even sprayed some quickstart spray in the air box to help. Fuel is getting to the spark plug, and the plug is sparking... I'm about to give up on it to be honest, have no clue why the bike suddenly completely failed. Any suggestions at all? : /

    Looking like its gonna be an expensive visit to the local garage.


  11. Just checked compression using my finger over the spark hole, blew my finger off so seems okay, what amount of compression is needed on these bikes? anyone know?
    I also just took the bike for a walk (bumpstart) without the HT lead so it wouldn't spark. The engine seems to turn over and move completely fine, and since replacing all the oil, it seems more lubricated and the engine turns over FAR easier than it did before. I'm about to take it to the garage, so although all my efforts have been for nothing, i will FINALLY know what went wrong.
  12. RPS

    RPS Member

    Not much help from me now I'm afraid but when you drained oil did it have any thing that it shouldnt have - like bits of metal. Maybe worth mentioning what area of country you are in just in case one of the forum experts is nearby and could have a look. Also have you thought of looking for a mobile bike mechanic in your locality who could
    take a look for cost of an hour of their time?
  13. Blazer

    Blazer Member

    If there is fuel getting to the cylinder and a spark to ignite it, then I can't see why it won't run. It could still be that a faulty cut off switch is stopping the engine from starting by stopping the injector from squirting petrol into the cylinder. If it is a kill Switch then it is unlikely to be the kick stand switch as it would still start in neutral, so I would check the clutch lever switch and the engine kill switch for any wires that may have come off before taking it to garage. You will need to open the switch gear housing to check whether any wires have come off behind the red engine kill switch, it has been known to happen.
    Last edited: Feb 19, 2017

  14. RPS there was nothing in the oil, came out smooth and black, although there wasn't much oil in there... about 200ml at most. I live about 20miles north of Cambridge. I hadn't thought of a mobile mechanic before, i'll look into it.

    Blazer I'm starting to think it surely must be a 'glitch' in electrics or wiring... everything on the bike is now flawless. Surely if the killswitch were engaged it would not turn over? It turns over fine.

    Thanks guys, it'll be interesting to get to the bottom of this...
  15. Blazer

    Blazer Member

    Sorry my bad, couldn't be the kill switch as you say, only last ditch attempt would possibly be the clutch lever switch then. Either something seems to be stopping fuel being squirted into the cylinder or there seems to be a mechanical issue. Good news is that the oil seemed fine so less likely to be a mechanical problem. If it does turn out to be a serious problem and a new or second hand low mileage engine needs to be fitted, and you want to save a load of cash, then it's an easy enough job to do yourself and normally takes around 3hrs.
  16. RPS

    RPS Member

    200ml of oil wasnt much to come out when it should hold nearly a litre. Maybe something has worn in engine as a result that prevents firing.

  17. Probably a mechanical issue then; already took out fuel injector and fuel is spraying in a fine mist, seems to be the same as other peoples' injector sprays on youtube, so no problem there...
    This is the problem boys:

    Bike full of good fuel -> Spark plug works perfectly -> Injector spraying fuel into combustion chamber -> Fuel IS NOT IGNITING. Like wtf? What can this actually be lol.
    Yesterday I was advised by a bike friend to pour a small amount of fuel directly into the spark plug hole (combustion chamber). I did this, took the spark out before hand obviously and tested spark again; still sparks perfectly.

    I put the spark plug back in, tightened it fully with all of the fuel in the chamber, started the bike and guess what? Turns over but won't fire, didn't even fire once which implies the fuel isn't being lit.
    Beginning to think it could be the spark plug not sparking under pressure once its in? Is this common?

    In response to you RPS, I understand it didn't have enough oil in it, furthermore it has had that little oil for at least a month or two... still thought as mentioned, nothing bad came out in the oil; and it came out smooth.

    Thanks guys, i'll keep you posted!

  18. Blazer

    Blazer Member

    It seems a bit confusing, but at least you've eliminated the fuel and spark so the only thing left would be the oxygen/air. You can check if the throttle body is allowing air into the engine, by removing the airbox. Once removed it should be possible to visually see if the throttle body is opening. Hope this helps :).
    Last edited: Feb 22, 2017

  19. I'm back.

    Okay, so the bike has been fully stripped and is now in bits, still trying to find the problem.

    It seems it has compression sometimes, but sometimes does not. Gonna have to take off the engine head and have a look... this is getting silly!

    Very sad, only needed the bike for one more month, as im now doing my big-boy test but am worried about doing my practicals after not being on a bike for like 3 weeks. I'll keep you posted, it will be quite a climax when i finally find the problem and what caused it.
    Last edited: Feb 28, 2017

  20. Any updates on this Luke? Sounds like a right ************er.:(

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