Yamah YP125R-XMAX 2010 Model - Unused since new and now having overheating problems.

Discussion in 'The Workshop' started by Phil 1899, Jul 24, 2021.

  1. Phil 1899

    Phil 1899 New Member

    At the beginning of the year (2021) I bought a 2010 Yamaha YP125R-XMAX.
    With only 1,038 miles, it was stored in a warehouse for ten years and in new condition. I done an engine oil and filter change, new air filter and engine coolant change. The problem I am experiencing is the engine cuts out once the temperature reaches half point on the gauge. There is also a loss of power once you accelerate over 40mph. The engine is overheating and I wonder if the engine oil that I used was the wrong grade; Motul 5000 4T SAE 10W40 MA2 Meets; JASO / MA2 / API / SL Specification. This is what I use in my Yamaha FJR 1300A. The scooter manual states engine oil grade; API Service SG type or higher. JASO Standard MA
    I have had the fuel pump out for inspection and the water pump and water thermost. I couldn't see anything obvious and don't know how to test these. Could a sensor be the problem?
    I would really appreciate anyone's assistance with this issue.
    Kind Regards, Phil
    Mark Emerson Trentham likes this.
  2. Mark Emerson Trentham

    Mark Emerson Trentham Well Known Member. Staff Member

    NSC110/ ET2.
    Had a look/10w40 checks out when ordering for your scooter,some problems mostly mentioned sensor,voltage regulator.
    Phil 1899 likes this.
  3. Phil 1899

    Phil 1899 New Member

    Hi Mark,
    Thank you for your communication and I have now ordered a voltage regulator / rectifier. I hope that you are correct as I am running out of considerations for what to check next. I removed and tested the water thermost in hot water and it appears to be working fine. I will post the results once I have fitted the voltage regulator.
  4. Phil 1899

    Phil 1899 New Member

    I got a replacement voltage regulator / rectifier but, this hasn't sorted out the problem. I wonder if one of the sensors is faulty or, maybe the throttle body. Is there anyone who can offer suggestions as to what might be wrong? Thanks.
  5. rfw

    rfw New Member

    Not familiar with the 2010 YP125 but I believe It's fuel injected so are there
    any error codes displayed on the panel when it goes wonky?
    I wouldn't worry about the oil right now and if it's not overheating you're probably fine
    The 10 year lay up would have me suspecting say a gummed injector getting sticky due to stale fuel.
    running a dose of injector cleaner through it wouldn't hurt.
    I dont have Yamaha error codes to hand but could dig them out
    I'd also check the grounding as this can throw sensors out .
    Phil 1899 likes this.
  6. rfw

    rfw New Member

    I am slightly confused by 'cutting out when temp gauge half way'
    and 'over heating'
    How can it over heat if it cuts out at half way up the scale?
    Phil 1899 likes this.
  7. Phil 1899

    Phil 1899 New Member

    Hi and thank you for your suggestions. I have added a dose of Redex to the fuel tank but, this hasn't appeared to have been any benefit. I removed the fuel injector and started it up to see if the petrol is spraying out and, it appears to be working fine. The engine run on idle fine until the temperature reaches about half position on the temperature gauge. It then stalls and when I restart it during normal running temperature, it constantly stalls. Would it be worth removing the fuel injector and leaving it overnight in a cup of Redex or something else to try and remove any gummed up old petrol?
    There are no engine management lights coming on so, nothing to offer me an indicator as to what the problem is... Frustrating, as the scooter looks brand new with just over a thousand miles on the clock.
    Last edited: Aug 10, 2021
  8. Phil 1899

    Phil 1899 New Member

  9. Phil 1899

    Phil 1899 New Member

    Previously, I removed the water temperature thermost and done a physical operating check using boiling and cool water. The thermost was working fine. However, when I fitted it, I didn't have the small air hole positioned correctly and, this allowed it to overheat. I sorted this out and it doesn't overheat anymore.
  10. rfw

    rfw New Member

    low miles
    10 year lay up
    starts ok until it gets warm then has conniptions
    No error codes displayed on eml

    The ECU will only display a fault if a sensor doesn't send a signal it 'likes'
    ie within certain parameters, so while the eml may indicate a bad sensor
    that still leaves plenty of scope for things to puzzle us

    Any forum advice can only best guess at best but we all like guessing games right?

    The thermostat just regulates the engine coolant temperature and works independantly of the ECU
    and is not monitored by it
    The engine temp sensor sends a signal to the ECU which uses this info ( and other stuff ) to calculate
    the amount of fuel to squirt in during the induction stroke.

    If the temp sensor is faulty or has a bad connection it may not be 'telling' the ECU the engine has warmed up and
    so it may be running rich which can make it cut out.
    You can usually smell a motor running rich

    Other heat related stuff could be the coil and possibly plug breaking down
    the ECU does not use signals or get feedback from the HT coil windings or plug
    so will not flash a code if they go wrong
    unusual for a low mileage bike though

    these are just various thoughts and guesses which may or may not be useful
    Never worked on the EFI YP125, My lad had the earlier carbed version
    and I now have the carbed YP250 but I have worked on a 2010 YBR125 which is EFI and
    presumably uses a very similar ECU in terms of base processes

    Despite low overall miles, it may still be prone to bad connections so would open,check and clean as many electrical connectors
    as I could just to be sure, if only to discount them.
    This in my opinion and experience should be an annual service item anyway.

    checking ground connections are all commoned up and the battery is being charged
    to a sufficient voltage is another check to do
    Phil 1899 likes this.
  11. Phil 1899

    Phil 1899 New Member

    Thank you for your quick response and your input and knowledge sharing is much appreciated.
    I have tried to purchase a Haynes Manual for my scooter but, they don't appear to publish manuals for individual models. All I could get was a generic manual but, this doesn't cover fuel injection scooters.
    I have already removed every electrical connection and gave them a squirt of WD40 and I also checked the coil connection and fitted a new spark plug. I will follow your suggestions and look at the engine temperature sensor but, you're right to say that there is plenty to puzzle us and keep us guessing.
    I will post my next attempt at sorting this out and hopefully get this resolved soon.
    Kind Regards,
  12. rfw

    rfw New Member

    I check the plug and note the colour
    If it's sooty this indicates over fuelling
    temp sensors usually have their resistance drop as they heat up
    so with no manual or specs to refer to, I'd measure the resistance when cold say 20C
    and do it again as the engine has warmed up.
    Some have a linear scale some not so cant give figures, but if it has no significant change
    in resistance at 40/50 C plus
    then I'd suspect its faulty.

    for reference
    Just been looking at the Yp400EFI wiring diagram
    and see the temp sensor is used by the ECU to calculate fueling and when to run the rad fan
    It has these specs
    20C 2320 to 2590 Ohms
    80C 310 to 326 ohms
    110C 140 to 144 ohms

    As Yamaha would be silly to design and invent a sensor
    purely for one model I reckon its not unreasonable for yours
    to have similar properties
    Phil 1899 likes this.

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