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Mcx 270 stumble

Discussion in '4 Stroke Turbos/Supercharger' started by Nitram, Feb 12, 2018.

  1. Nitram

    Nitram Newbie

    Messages:
    6
    Location:
    Calgary
    Country:
    Canada
    Snowmobile:
    2008 Yamaha nytro mtx mcxpress 270
    hey guys still trying to figure out my stumble on my 08 mtx nytro with mcx 270 turbo. At idle it will fluctuate up and down. Not really a rough idle. But if I rev it up a bit just enough that the sled won’t move it runs horrible. Really rough and like a pretty bad miss. Could it be a boost leak? Secondary injectors? I installed a brand new set of plugs and didn’t change anything. Top end power still seems to be there and no stumble or miss. Also seems to hesitate for a quick second as I give it more throttle. Any help is greatly appreciated fellas. Thank you!! Cheers!!
     
  2.  
  3. M7000

    M7000 Newbie

    Messages:
    20
    Location:
    Karasjok
    Country:
    Norway
    Snowmobile:
    M7000
    Im having a similar issue with my mcx 190 kit on my M7000. When doing high rpm it works great, but when driving really slow, the rpm will flicker even though im keeping the same throttle position.

    I know on my sled there is some exhaust leaking between the muffler and turbo, because mcx doesnt use a gasket there. And since im not running a snorkle kit, the turbo could be sucking in exhaust and causing the rpm to flicker when idling/driving very slow.

    Another detail is the battery might be a bit low, since when i was installing the turbi i had some issues with vacuum hoses connected wrong - and thus had to try many start-ups.

    First im going to adress the exhaust leak to see if that is causing the problem.
     
  4. mbarryracing

    mbarryracing TY 4 Stroke God

    Messages:
    1,697
    Location:
    Springville NY
    Country:
    USA
    Snowmobile:
    2006 Yamaha Attak Turbo
    2015 SR Viper RTX-DX
    1996 Vmax 600XT
    Do you have an AFR gauge? What is the AFR doing when it's stumbling at a high idle below engagement?
    Does MCX use an TPS signal? Wonder if that is screwy.
     
  5. Nitram

    Nitram Newbie

    Messages:
    6
    Location:
    Calgary
    Country:
    Canada
    Snowmobile:
    2008 Yamaha nytro mtx mcxpress 270
    I just ordered an exhaust flex pipe and fixed a couple of boost leaks. Next I will check the secondary injectors in the intake plenum to see if they are leaking
     
  6. Nitram

    Nitram Newbie

    Messages:
    6
    Location:
    Calgary
    Country:
    Canada
    Snowmobile:
    2008 Yamaha nytro mtx mcxpress 270
    I
    ahh crap I don’t have an afr gauge. Been on my to do list to get one
     
  7. M7000

    M7000 Newbie

    Messages:
    20
    Location:
    Karasjok
    Country:
    Norway
    Snowmobile:
    M7000
    D
    did you figure out anything yet? I havent gotten around to adressing my issues yet. Been cold af up here :)
     
  8. Nitram

    Nitram Newbie

    Messages:
    6
    Location:
    Calgary
    Country:
    Canada
    Snowmobile:
    2008 Yamaha nytro mtx mcxpress 270
    Not yet bud. Just picked up my exhaust parts yesterday. Took forever to get here. Gonna get it back together tonight and try it. Once I get the exhaust back together and the tank back on I’m gonna run it with the secondary injectors out and see if they are leaking. Kinda thinking that’s the issue. Will keep you posted!!
     
  9. Nitram

    Nitram Newbie

    Messages:
    6
    Location:
    Calgary
    Country:
    Canada
    Snowmobile:
    2008 Yamaha nytro mtx mcxpress 270
    Boost leaks fixed. New exhaust flex pipe installed and still no improvement. Seems to only get bad once the sled warms up. I’m lost. Added a video. I really hope someone can help
     

    Attached Files:

  10. M7000

    M7000 Newbie

    Messages:
    20
    Location:
    Karasjok
    Country:
    Norway
    Snowmobile:
    M7000
    Tried fixing my exhaust leak with some heat bandage stuff between the muffler and the turbo. Im not noticing that much rpm fluctuation while driving now.

    But what i do notice is that when im driving and if i let go of the throttle, the rpm will drop all the way to 1100rpm. Wonder what it is doing that?
     
  11. M7000

    M7000 Newbie

    Messages:
    20
    Location:
    Karasjok
    Country:
    Norway
    Snowmobile:
    M7000
    Figured out the bogging when letting go of the throttle. I tightened the drive belt. Apparantly if your belt is too slack it can cause bogging.
     

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