Home Forums TaG Rotax Max Micromax fuel delivery and rev problem

This topic contains 9 replies, has 6 voices, and was last updated by  Craig Foster 3 years, 7 months ago.

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  • #50965

    Craig Foster
    Participant

    Please help! I have a 2015 micromax Evo and am still not able to exceed 9800 RPMs. I’ve gone between a 100 to 105 Main jet.  Needle is set at P2 and air fuel idle ratio is two turns out on the screw. Sporadically, it acts as if it vapor locks. It dies at low rpm’s or has no low end power, top end seems to be OK.  Fuel is leaking out of the Mikuni pump at the gasket. Not sure if these issues are related.  Any help from those that are getting performance from the evil  (oops I meant EVO) micromax is greatly appreciated. Thanks

  • #50971

    tony zambos
    Participant

    Know zippo about EVO’s. Start with what you know is wrong, the fuel pump.

    LAD Specialties customer / tony kart / rotax / kt100

    • #51012

      Vincent Ciolino
      Participant

      I would start with replacing/rebuilding the fuel pump.  Are you using the throttle stop?

  • #51048

    Mark Traylor
    Participant

    go ahead and replace the fuel pump gasket but if it wont  pull out of the corners well you are too lean.   And the carb set up you have said is pretty lean.

  • #51049

    Mark Traylor
    Participant

    BTW…what is the experience level of your driver?

  • #51091

    Craig Foster
    Participant

    Thanks Mark and Vincent, first I am using the throttle stop (33 millimeters) spacer that was supplied in the update.  Seems for 2000 feet above sea level and 80° a 102 to 105 jet should be about right?  Driver set track record in last 2 races.  I just felt 11,000 RPMs would be possible, as this track has two straightaways that demand high RPM…

  • #51114

    Steve piggott
    Participant

    If you can get 11000 out of a micro than I’m doing something wrong, we never get above 9600 under load.

  • #51151

    Christian Fox
    Participant

    On a track with a long straight, a good Evo Micro can hit close to 11,000, and a good Prevo can get 10,500. There is a big difference between good and average with regards to Micros. Depending on the track, max rpm has a lot to do with how your driver enters the straight. Did you race Micro prior to Evo? If so, what rpm did you hit then?

  • #51174

    Mark Traylor
    Participant

    Craig,

    my upgraded micro has been hitting 10,800 regularly at our track with a pretty long back straight.   Don’t worry about what the jetting should be.    Follow the signs in the tune.   What you described makes it seem lean.   Read the pipe.   I have found the Evo, while finicky, to be very predictable and it behaves logically the way that you would expect a 2t to tune.   The old carb seemed quite counter intuitive to me relative to past 2t engines I tuned.

  • #51186

    Craig Foster
    Participant

    Thanks Mark, the plug is light brown and the pipe is just about right, certainly not wet.  Thats what has been confusing me. This is a 2015 Evo, not upgraded Prevo. I’ll keep playing with the Jets and the oxygen ratio.  Air filter is clean and not saturated. Thanks again, I’ll keep trying and report back.

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