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YZF R125

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by InvalidUser, Oct 28, 2014.

  1. Hi All,
    Ok I've decided to start a thread about the problems I've been having with my Yamaha YZF R125 (2010) to hopefully help those who have similar/same issues with their R125's and also ask for help if anyone knows anything. I've spent quite a few hours looking into the problems on the net and the only consistent issues seems to be the Fuel Pump but before that this is how things went;

    When I first checked her out she looked great and pretty well taken care of. I had asked the owner to cold start it when we got there and she didn't have any problems at all.
    I then rode her about 40-50 minutes home from the city without any issues at all and managed to stall her right in my driveway (I hadn't ridden in years except for my pre-learners and my driveway is made up of a mix of gravel, dirt, grass, a great ditch and concrete).
    And thus began the problems... since that point she's had trouble starting.
    Now from experience with my past bikes and what I know about cars I did the following;

    1. I recharged the original battery first - started the first time then wouldn't start
    2. Then changed it for a whole new one - started and thought it was fine.
    Then it wouldn't start.
    3. Changed the spark plug - fired up first go - thought the problem was solved but the next day it was gone again.
    4. I've ridden to work and back thinking it was fine but this doesn't seem to be the case.
    Now it's been about 10 days since I've had her and I'm starting to notice that there is a certain noise she makes when I turn the key to 'ON' and activate the kill switch. It's a whirring type of sound and I've read that this is her priming the fuel?
    Anyways I'm noticing this sound isn't always happening and most of the time when it doesn't happen she doesn't start and when she does she Cranks, Turns over and then attempts to idle but always dies out. A few times I've been able to save her with some revs but it usually ends up dying.
    What I've also noticed now is that during the day when I wake up (around 12-1pm) she cranks, turns over then dies.
    At night after work (230-3am) she cranks, starts and idles fine (the whirring sound is present).
    I've got a $50 fuel pump on order from ebay because Trooper Lu's quote me $600 and a mobile mechanic $650 to get the fuel pump replaced. Given that the price is quite high and the problem isn't even correctly diagnosed yet I decided my money was better spent learning more about my bike.

    Sorry I know it's a lot to read but I'm just wondering is it likely the temperature is the main thing affecting it's ability to start at 3am and not start at 12pm? It has gotten quite hot in and around the area lately.
    Today as the sun went down (around 6pm) she cranked and spluttered but wouldn't idle properly when all day she wouldn't even start.
    At 11pm when I gave it another shot she spluttered into life without any issue.
  2. Could also be the fuel pump relay. Sometimes these get affected by heat and give intermittent problems. Check to see if your bike has one and replace it if the fuel pump you bought doesn't fix the problem.
  3. The lack of whizzing up when you turn key and run switch to "run" means the fuel pump isn't priming, and hence why it won't start, but when the whizz is there it fires no problem.

    Heat is very very unlikely to be the cause of the issue from a cold start regardless of time of day. The pump connection plug, harness, or relay is where you should be looking.
  4. Are they prone to vapor lock? Also take a look at the fuel filter maybe?

    I am no mechanic but that's what I would be checking if it was my bike along with the electrics to the pump.
  5. Just googled vapor lock and it does sound like a similar issue?


    Is the bike parked under cover or out in the sun? Also have you managed to put new fuel into her yet or are you still using the same fuel that was put in when you bought it?
  6. I vaguely remember Yamaha having the odd issue with fuel pumps on their 125 scooter, which were prone to intermittent jamming. Your YZF- R125 might use the same pump. Replacing the pump fixed a scooter I was having similar issues with. Maybe your pump has had a bad batch of fuel go through it, swelling the plastic impellor. By bad, I mean ethanol, or some other additive that some dodgy servos have been known to add to their fuel.
    That $600 price you were quoted may have been for replacing the complete pump assembly, which is sometimes all that is listed in the parts catalogue. I called Yamaha regarding the scooter, and someone there had found a part number for a pump on an outboard motor, that was the same and was sold just by itself, and was much cheaper.
  7. @BugzR34 - Will definitely look into that after I try this new fuel pump. It's supposed to arrive in a week or 2s time.
    @TWEET - I'm not sure but it's just what I've found so far.. today was a warm day but had a nice breeze and she started fine - actually went up to homebush for a ride around the L's practice area there
    After the 30-40min ride up and some practice my mate stalled it and it wouldn't start up again there. Gave it about 10 minutes thinking the heat from the ride and practice might affect it and it started up fine again.
    @Grrila - Not sure about this one, I'll need to do some reading, I just poured some fuel last night but the tank wasn't fully empty. I poured 98. It used to be kept in an underground parking lot before I bought it but now it sits mostly outside - no cover (my dog wrecked my cover)
    @Tinkerer - I found some stuff on the R15 also having fuel pump issues and some r125 (2008-09) had a recall regarding this which is the main reason I suspect its the pump. The quote from Trooper Lu's said " ..the fuel pump is not sold separately the only way you can buy it is by purchasing the whole tank.."(excerpt from my email)
    Thank you to everyone for posting though, hopefully I get it fixed no asap, your thoughts are appreciated! =D
    I have had some time out on her though and I'm not as frustrated as I have been since the ride.
    I've noticed I blab on a bit don't I...