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I don't remember piss revving my old dirt bikes to check tune

Discussion in 'Chainsaws' started by Duane(Pa), Mar 3, 2019.

  1. Duane(Pa)

    Duane(Pa) It's the chain...

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    That was a lifetime ago, but I think I always piss revved the old Homie SXLA to set the H screw back in the day. I practiced hole shots a bunch on the YZ, and I suppose something would have come unglued if it wasn't four stroking. Memory is a little fuzzy of those days of yore. (no idea why that would be)
     
  2. a. palmer jr.

    a. palmer jr. Super OPE Member

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    I've owned several 2 stroke dirt bikes, the latest being a Yamaha YZ490 and I don't remember setting anything but the idle speed. I don't think those things had H and L screws, I believe they were fixed jet carbs with a needle going down into the H jet. I think you could buy different jets for them if you needed to..
     
  3. Terry Syd

    Terry Syd Pinnacle OPE Member

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    The carbs on the bikes had an air bleed jet in the main jet system. The air bleed allows much better mixture control and will prevent the carb from going too rich as the revs go higher.

    The best way to keep the engine from over-revving was to keep a load on it. However, newer ignition modules do have a rev limiter built in.
     
  4. Marshy

    Marshy WFO Cutting

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    This
     
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  5. shadco

    shadco Super OPE Member

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    Wouldn’t have done that, long straight wide open in top gear, throttle chop and clutch in at the same time. Pull plug and read the plug. My old Maico would probably thrown a rod with a piss rev.

    .
     
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  6. stihl_head1982

    stihl_head1982 Here long time

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    yes, the days of YZ dirt bikes and MX dirt bikes. I remember. Me thinks I'm telling my age.
     
  7. Duane(Pa)

    Duane(Pa) It's the chain...

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    It’s all coming back to me... I remember moving the needle up and down by repositioning the little e clip. And plug reading. Different size jets in a kit that bigger dogs than me would have at the track etc.
     
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  8. Marshy

    Marshy WFO Cutting

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    The needle (E) clip height adjusts mid throttle mixture. Main jet is WOT mixture.

    Here, this is easier to read than words...
    hqdefault.jpg jet-chart.jpg
     
  9. USMC615

    USMC615 God...Country...Corps

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    My first dirt bike was a brand new Honda XR75...if we're gonna be giving away our age. lol

    Had a few as I got into my teen years and a little older...KX125, YZ125, RM250. Been a year or three since I've rode and cut up on one...my body don't heal quite like it used to!
     
  10. shadco

    shadco Super OPE Member

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    My race stable looked like this.

    73 Husky CR125
    74 Kawasaki KX125
    75 Maico 250
    77 Maico 250
    79 Kawasaki KX125A4
    74 RD 350
    72 Yamaha TR350.

    Those were fun days.

    .
     
    Last edited: Mar 4, 2019
  11. Duane(Pa)

    Duane(Pa) It's the chain...

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    I remember it like it was yesterday. Wait...no I don't lol
     
  12. stihl_head1982

    stihl_head1982 Here long time

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    My cousin had the XR75. Things he did with that little sucker with me on the back made my hair stand up!
    I had a MX360 (last dirt bike)
    upload_2019-3-4_19-15-58.jpeg
     
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  13. Duane(Pa)

    Duane(Pa) It's the chain...

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    I loved the sound of those bikes! (360) Especially when they were going down a long shallow hill.
     
  14. stihl_head1982

    stihl_head1982 Here long time

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    Nice line up.
     
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  15. 00wyk

    00wyk Pinnacle OPE Member

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    I have some very fond memories on a YZ125. All the piss-revving I did was right before I ended up being thrown from the bike.
     
    Last edited: Mar 5, 2019
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  16. NCPT

    NCPT Super OPE Member

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    I still ride. KTM 300 with a Lectron carb. I haven't messed with the carb in a while and cant really remember how it works but there are no jets to mess with, just a metering rod. I have the stock Keihin carb also and it is jetted real nice, actually gives the bike more arm ripping power. The Lectron delivers a nice linear power, great for trail riding.
    20180708_172401.jpg
     
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  17. stihl_head1982

    stihl_head1982 Here long time

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    Very nice ride.
     
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  18. shadco

    shadco Super OPE Member

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    Since there isn't a Like that a lot button I'll just put this here.

    I like that a lot.
    .
     
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  19. NCPT

    NCPT Super OPE Member

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    Thanks. I've rode dirt bikes since I was 8 or 9, most have been 2 strokes, never really wanted one of the newer 4 strokes. These 300's are so cool, you can tune them to be a tame trail machine or they can be tuned to rip your arms off....this one is tamed down.
     
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  20. NCPT

    NCPT Super OPE Member

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    The zip tie stitches in the rear fender are one reason why I softened the power delivery lol.
     
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