505SX Rancho Mod help
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  1. #1
    Junior Member Rookie
    Join Date
    Jan 2019
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    9

    505SX Rancho Mod help

    So my 505 a lot of the times is hard to start. It just turns over and give it little throttle to help and finally starts. Has a hard time starting and someone mentioned doing the rancho mod.

    What exactly is that? I assume it will help with starts. I live and ride as sea level and my quad it all stock. Thanks

  2. #2
    Senior Member KTMATVHQ Guru
    Join Date
    Dec 2008
    Location
    Billings, MT
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    1,092
    It consists of drilling the accelerator pump nozzle orifice to a larger size, drilling and tapping the float bowl to accept a leak jet for the accelerator pump, changing to a Honda HRC needle (that is no longer available through Honda), and putting an o-ring around the accelerator pump linkage. It mostly focuses around improving throttle response and eliminating a bog some people experience when stabbing the throttle. I don't see it affecting the starting ability of the machine.

    Other things I would look at:
    Making sure the carb is clean. Especially the pilot circuit and fuel screw passages.
    Correct jetting/fuel screw setting.
    Correct throttle cable free play. If it is a little too tight the throttle safety switch won't let it start unless you open the throttle slightly.
    Fresh fuel and a new spark plug. I've had old plugs cause hard starting issues before but run fine otherwise.
    Inspect the intake boot between the head and the carb for cracks. Often you have to remove the boot and look from the inside to see them.
    Inspect the auto-decompression device on the cam and make sure it's working properly and there is no worn spot on the finger follower that it presses on.
    Mine:
    2017 Husky FX 450
    2009 505 SX
    2008 525 XC-modded for mx (currently 450 cylinder)
    Dad's:
    2009 450 SX
    2008 540 XC

  3. #3
    Junior Member Rookie
    Join Date
    Jan 2019
    Posts
    9
    Okay thanks man I will do that!


    Quote Originally Posted by quad97 View Post
    It consists of drilling the accelerator pump nozzle orifice to a larger size, drilling and tapping the float bowl to accept a leak jet for the accelerator pump, changing to a Honda HRC needle (that is no longer available through Honda), and putting an o-ring around the accelerator pump linkage. It mostly focuses around improving throttle response and eliminating a bog some people experience when stabbing the throttle. I don't see it affecting the starting ability of the machine.

    Other things I would look at:
    Making sure the carb is clean. Especially the pilot circuit and fuel screw passages.
    Correct jetting/fuel screw setting.
    Correct throttle cable free play. If it is a little too tight the throttle safety switch won't let it start unless you open the throttle slightly.
    Fresh fuel and a new spark plug. I've had old plugs cause hard starting issues before but run fine otherwise.
    Inspect the intake boot between the head and the carb for cracks. Often you have to remove the boot and look from the inside to see them.
    Inspect the auto-decompression device on the cam and make sure it's working properly and there is no worn spot on the finger follower that it presses on.

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  5. #4
    Senior Member KTMATVHQ Member
    Join Date
    Nov 2015
    Posts
    364
    Quad97 hit it excellent.
    Only things I want to add is that sounds like a valve adjustment issue. Very very common on power port machines across the board. Starts hard or not at all, bump starts fine.
    Lastly a slightly weak battery may not turn it over fast enough to start it. Since you can get it to start by slightly tapping that throttle I bet it’s fine but wanted to put it out there.


 

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