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  • Fork Oils????

    Hey, just one question, has anybody changed the oil in the forks on their Hyosung 250 or any other bike to make them a bit stiffer?

    The forks on my bike seem to bottom out very easy even at low speeds. Any suggestions would be good.
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  • #2
    Have you made any adjustments to the preload? If you're fussy about suspension, make a booking to go see Marty Moose.
    PSB Roller - http://soundcloud.com/talon

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    • #3
      Originally posted by chesty1984 View Post
      Hey, just one question, has anybody changed the oil in the forks on their Hyosung 250 or any other bike to make them a bit stiffer?

      The forks on my bike seem to bottom out very easy even at low speeds. Any suggestions would be good.
      Hi dude,

      Yes, I am a religious fork oil changer, just did the 1250 Bandit and the Buell Firebolt.
      Does the Hyo have any spring preload adjustment [it may look like a large nut on top of the fork legs] if so, add more preload, screw the adjuster down to put more tension on the springs.
      If you have no adjusters, you need to change the fork oil, buy adding a heavier weight oil, it will firm the forks, and buy adding slightly more oil, the forks resist bottoming out.
      And before you put the fork caps back on, you can add spacers on top of the springs to stiffen them up. Put bike back together and go for a ride and you will wish you had done it ages ago.

      I am in Tuart Hill if you need to me to have a look at it !!!

      Regards buelllord
      Women are like motorcycles, they should be ridden hard and kept well lubricated ...

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      • #4
        As the others have said, bottoming out is preload/spring tension.

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        • #5
          Originally posted by druu View Post
          Have you made any adjustments to the preload? If you're fussy about suspension, make a booking to go see Marty Moose.
          Originally posted by Desmogod View Post
          As the others have said, bottoming out is preload/spring tension.
          I'm pretty sure that my forks don't have an adjuster for the preload.
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          Make sure you do what it says

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          • #6
            Originally posted by buelllord View Post
            Hi dude,

            Yes, I am a religious fork oil changer, just did the 1250 Bandit and the Buell Firebolt.
            Does the Hyo have any spring preload adjustment [it may look like a large nut on top of the fork legs] if so, add more preload, screw the adjuster down to put more tension on the springs.
            If you have no adjusters, you need to change the fork oil, buy adding a heavier weight oil, it will firm the forks, and buy adding slightly more oil, the forks resist bottoming out.
            And before you put the fork caps back on, you can add spacers on top of the springs to stiffen them up. Put bike back together and go for a ride and you will wish you had done it ages ago.

            I am in Tuart Hill if you need to me to have a look at it !!!

            Regards buelllord

            Yeah there is no adjusters on my forks so i'm pretty sure that a heavier oil is in order. What grade of oil do you think would be better???
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            Make sure you do what it says

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            • #7
              Not neccesarily. If you don't have preload adjusters, you can use shims or spacers to provide the required preload.
              PSB Roller - http://soundcloud.com/talon

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              • #8
                i think you can use auto trans fluid.
                Need your suspension tuned? See Marty MOOSE! | Need something out of the ordinary? See Gav (GD Engineering)!

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                • #9
                  If your forks are bottoming, a heavier oil is NOT the way to go. The oil in the forks is used for damping, it forces through small holes to control the speed the forks compress or rebound, the spring is what you need to change to stop it bottoming, take it to russel at dynotime or contact marty moose on here for all your suspension needs.
                  Instaed of adding thicker oil, which makes it harder to force through the small holes, which in turn heats up, making the oil thin out, and you end up with suspesion that behaves differently all the time, put some more oil in each leg, that reduces the air gap which will make them a little stiffer as oil wont compress where the air that was in there does.
                  Take it to Marty, he will help you out and explain what he is doing and why.

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                  • #10
                    Originally posted by chee View Post
                    i think you can use auto trans fluid.
                    Is ATF any heavier then whats already in there?
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                    • #11
                      Originally posted by druu View Post
                      Not neccesarily. If you don't have preload adjusters, you can use shims or spacers to provide the required preload.
                      do you know where can i get some spacers from?
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                      Make sure you do what it says

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                      • #12
                        Originally posted by Sean'o View Post
                        If your forks are bottoming, a heavier oil is NOT the way to go. The oil in the forks is used for damping, it forces through small holes to control the speed the forks compress or rebound, the spring is what you need to change to stop it bottoming, take it to russel at dynotime or contact marty moose on here for all your suspension needs.
                        Instaed of adding thicker oil, which makes it harder to force through the small holes, which in turn heats up, making the oil thin out, and you end up with suspesion that behaves differently all the time, put some more oil in each leg, that reduces the air gap which will make them a little stiffer as oil wont compress where the air that was in there does.
                        Take it to Marty, he will help you out and explain what he is doing and why.
                        Cheers Mate, will do
                        sigpic

                        Make sure you do what it says

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                        • #13
                          Originally posted by Sean'o View Post
                          If your forks are bottoming, a heavier oil is NOT the way to go. The oil in the forks is used for damping, it forces through small holes to control the speed the forks compress or rebound, the spring is what you need to change to stop it bottoming, take it to russel at dynotime or contact marty moose on here for all your suspension needs.
                          Instaed of adding thicker oil, which makes it harder to force through the small holes, which in turn heats up, making the oil thin out, and you end up with suspesion that behaves differently all the time, put some more oil in each leg, that reduces the air gap which will make them a little stiffer as oil wont compress where the air that was in there does.
                          Take it to Marty, he will help you out and explain what he is doing and why.
                          Chesty,

                          I apoligise for the amount of crap you have to wade through on this site, and don't use ATF.

                          You need slightly heavier oil than what is in it. if your bike comes with 10 weight for example, I would try 12.5 as a starting point and over fill each leg by about 5-10mm. To add spring preload, 10 or 20 cent peices work well depending on the leg diameter.

                          Regards buelllord
                          Women are like motorcycles, they should be ridden hard and kept well lubricated ...

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                          • #14
                            Are you suggesting sean'o is talking crap?

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                            • #15
                              fork oil viscosity changes the rate at which oil wants to be pushed back and forth through the valves in your forks. as you go over bumps, the forks will move up and down to absorb the shock (hence why they are called shock absorbers). putting thicker fork oil into your forks will make the oil pass through the valve at a much slower rate (because it is thicker - ed. no duh) and you wont hit the bottom of your fork travel as quickly (or that's how it works in theory). that is a flawed way of fixing the problem tho

                              from what i'm told, the best way to stop bottoming out is to change they way the forks compress. you have an air gap in your forks which acts like a spring. physics 101 tells us that while liquids dont compress, gases can be compressed. if you're bottoming out (ie. your damper rods are hitting the bottom and can go no deeper), you can reduce the air gap. you will have to break a lot harder with a lot more force to compress that smaller amount of air enough to be bottoming out. how much of an air gap should there be? check the manual and that will tell you the standard size. if you have the standard size and it is bottoming out, it becomes a play-it-by-ear game. you will have to add extra oil bit by by and see what an influence it has on your travel

                              the other solution is to put a stiffer spring in place of the original one you have there. more expensive than fork oil, can upset the handling more (if you don't know what you're doing) and i'd recommend you see a proper suspension guy like Russel Farrow or Russell Speak if you want to do that (rather than your average bike shop)

                              with the thicker fork oil solution, i had that one given me. i moved from 10Wt to 20Wt and it did slow the way that the fork moved (which not a good thing for a trackday bike). it didnt bottom out as quickly (it still bottomed out under hard braking), but it made my front end feel like it was made out of cement. heavier weight fork oil tends to mask any handling issues you have by limiting the feedback that the front end gives you
                              Originally posted by Pkunk
                              It is a SCIENTIFIC FACT that all blondes with good bodies look 80000000000000000000000x without blonde hair

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