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This topic contains 10 replies, has 4 voices, and was last updated by  tony zambos 5 months ago.

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  • #24500

    PJ Lyda
    Participant

    I just purchased a Rotax Senior motor just to play around with and need some general info about the motor. Like how high do I rev the motor and how hot to make the motor. One last thing I need to know about is the jetting I have heard this is the problem with some of the rotax and just want the basics on it.

    Thanks

    #24504

    tony zambos
    Participant

    max rpm’s about 12500.  that’s the peak of the power curve but it can be rev’ed to 14k.

    temp between 140 and 160.

    jetting with a 158 main jet should be safe.  watch the plug and exhaust color.  black is too rich and white is way too lean.  Look at some of the jetting programs out there.

    power valve should kick in around 7000 rpm’s.

    Down load the FR125 Operators manual.  It’s good, just don’t believe the jetting chart.

    #24508

    PJ Lyda
    Participant

    Thanks That Really helped

    #24510

    Mike Bray
    Participant

    I have a weather station and a spreadsheet I use for jetting, works great.  Just let me know if you want the spreadsheet and I’ll send it to you.  These sites might help you some with basic information.

    http://www.internationalkarting.com.au/files/downloads/dispelling_the_rotax_myths__complete.pdf

    http://www.karting1.com/new-ThePreparation&JettingoftheRotaxCarb.pdf

     

    #25028

    Joe Bowen
    Participant

    So after attending my first race last weekend and looking for nothing but “Seat time” I quickly learned that with a kart not running or tuned for the weather conditions made for a long day! My kart ran great on Friday with a 160 main jet NGK BR9 plug but then Saturday temps were cooler and the kart wouldn’t hit high RPM (I call it power band like a dirt bike) until at least 100′ further down the straight than the other karts. So I tried a smaller jet 158 but that wasn’t enough. I was also told the spark plug I was using wasn’t optimum for the Rotax so I question What plug is best and can you use a hot or cooler plug to tune the engine like the main jet?

    #25029

    tony zambos
    Participant

    What were your max rpm’s on both days and did you run the same gear ratio?  You can tune with plug temps, but the main jet will get more results.  Hotter plug on cold days and a cool plug on a hot day.  Check your power valve blade for smooth operation.

    #25031

    Joe Bowen
    Participant

    What were your max rpm’s on both days and did you run the same gear ratio? You can tune with plug temps, but the main jet will get more results. Hotter plug on cold days and a cool plug on a hot day. Check your power valve blade for smooth operation.

    I’m not sure on the RPM’s the only sensor I had was temp. I’ll have RPM sensor next race in a week. What brand plug does the rotax engine like? I plan on having a wide jet range to adjust, Plugs and gears

    #25032

    Mike Bray
    Participant

    Start with a Denso IW27 plug and tune from there.

     

    #25034

    tony zambos
    Participant

    Joe,

    TIP:  One of the best tools you can bring to a track is a note book and a pencil.  At least per sessson,  keep track of max RPM’s, gearing, chassis set up and lap times.  Purchase a weather sation to track barametor pressure, temperature and humidity.  Once you’ve those settings, when the weather conditions are similar, I’ ve an idea for jettng.

    You didn’t mention the type of gauge you’re using.  Recommend a Mychron 3 or 4 to capture RPM’s and lap times to begin with.  A water sensor would be nice to have so you can tell if the engine is running at the right temp. You will then have the oportunity to load that information into Race Studio and be able to review the data between weekends.

    #25045

    Joe Bowen
    Participant

    I have the Mychron 3 with the temp sensor that threads into the cylinder head on the Rotax. I’ll have a RPM sensor by next race. I know last race it was temping at 114-118 from what I’ve read that’s on the cool side

    #25048

    tony zambos
    Participant

    When you run the RPM wire, kept it away from the water sensor lead to prevent interference.  You could safety run 25 degrees warmer.  Bring some masking to block off the radiator, if your track approves, and block off part of the radiator.  Keep an eye on temp and pull off tape as necessary. Or set the alarm function in the M3.

     

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