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Progressive fork spring spacer cut length?

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    Progressive fork spring spacer cut length?

    Ok dudes got the fork apart and did the Dave moss dump and run with 15w fork oil(only 12oz. 350cc in each??) and new progressive springs. P.S.35 year old fork oil will bout make ya puke! Lol So the next step...cutting the spacer. I've seen 2.5 inches and 3.5 inches, but measured the inside and it about 3 inches to the beginning of the inner cap threads. So...??? Does more spacer mean more preload? And it's 3.3in to the top of the fork with washer in. I'm just doing spirited Georgia Mountain runs,no track. Looking for some advice here, I don't wanna screw these spacers up. If I go above the crown I'm afraid I won't get it closed. Any and all help is much appreciated.

    #2
    The minimum effort you are looking for is to set spacer length so when everything is inside the forks, except oil, the spacer is flush with the stanchion top on fully extended forks and the stock fork tops will then provide adequate preload - as you do not provide specs on the spring rate, this is the level to work with...

    When you have made spacers to the right length, use 150mm oillevel with springs and spacers out of the forks and the forks fully compressed.

    Ride and adjust as necessary.

    Or you could read some of the threads on fork setup and just put a lttle effort into it. Or not.

    Comment


      #3
      Ok thank you for your help. There's only one part number for progressive springs so there's no spring rate given,sorry.

      Comment


        #4
        Originally Posted by racerboy4 View Post
        Ok thank you for your help. There's only one part number for progressive springs so there's no spring rate given,sorry.
        What is the length of the spring?

        FYI - PVC pipe makes for perfectly adequate spacers. Cheap and easy to cut.
        ASMA #139

        Comment


          #5
          Originally Posted by Talon View Post

          What is the length of the spring?

          FYI - PVC pipe makes for perfectly adequate spacers. Cheap and easy to cut.
          This..

          And it's always a bit of an effort to get the forks back together for me. But worth it.

          As Jan eluded to, there are a lot more veriabales here to consider if you want to get it "right" straight out the gate, but the best move is to put something together and don't be afraid to adjust as needed to get decent sag #'s.

          Do you have fork caps with preload adjusters? Of not, spend the $30.

          If you have a real soft spring you may find yourself adding too much pre load to get the appropriate rider sag, which can lead to some iffy top outs when the rider de-weights themselves.. so careful.

          knowing what spring you have is a valuable thing to know. Where did you get the springs?
          Don't spend money and buy, spend time and learn.

          Comment


            #6
            Well um I actually bought from a member on here in 2010 Lol . They are progressive brand. Idk what the kg rate is, they only offer the one part number for the hawk. I did use 15w Maxima oil, and cut the spacer at the top of the tube as Jan said to. I did have a issue though. I watched a Dave Moss video called a dump and run. He said to replace the oil with the same cc's as you removed. I pumped the forks as I held it over the ratio rite cup. I only got 12oz. (350cc)per fork. I have downloaded the manual and it says it should be around 14.8 oz. Now I'm sure it's the original oil because holy God the smell!! Will the oil evaporate or something? Both forks had 12oz. In them. I mean I can simply pop the caps back off and put the 2.5 oz. per fork in right? And these preload caps you speak of? Can I just order pre 94 600f2 caps Oem? Like Partzilla.com? Are they plug and play? If so I'll definitely order them! Thanks for any help getting the old girl back running..almost done

            Comment


              #7
              Easy part: the fork (preload) caps will work.

              Less than easy part (fluid volume):
              Think of this like jazz music. It's not about the notes you play: it's about the notes you don't.

              You're not really filling the forks with a volume of oil. You're leaving behind enough air to act as a spring.

              What you need is enough oil to make sure that the emulators or cartridges are always and completely immersed. (If you're not running emulators or cartridges then stop reading now and order some.)

              The remainder of the volume inside the fork is air. As the fork compresses, the internal volume decreases and the air compresses.

              This amounts to the "free volume" being an "air spring." The more you compress it, the more it pushes back.

              Changing the volume of air to compress is another thing you can tune. A large volume is a bigger, softer spring. You can only make this so big -- as stated earlier, the entire emulator/cartridge/damper rod (boo) has to be always in oil.

              The smallest volume would be zero. A fork completely filled with oil will be virtually incompressible. The spring will be unable to do its job because the oil volume won't let the spring compress. The spring would not be "suspending" the front end at all.

              Somewhere in the middle, you have a volume of air that will increase pressure as the volume decreases, and will push back on the fork (just like the spring). It will be at a different rate than the spring. A larger volume will be softer and a smaller volume will be stiffer.

              Measuring a set amount of fluid to fill the forks is a convenient metric, but the end game is a volume of air.

              Lots of factors affect what volume of an air spring you'll end up with. Thinner diameter spring steel will occupy less volume than thicker.
              Tighter coils will occupy more volume than looser.
              Progressively wound springs will displace more volume if put in with the tightly wound coils facing down and less with them facing up.
              You could even put your spacers BELOW the springs and they would occupy a different volume. MORE if PVC, almost nothing if thin walled aluminum.

              The point here is that there is no magic number for the amount of oil to fill your forks with. There is a volume of the fork that you don't want filled with oil (an incompressible substance) and this is so much harder to measure when you're rebuilding a fork than it is to pour a set amount of oil into the fork.

              My main point here is: do whatever Jan says to do and hopefully he'll correct all the B.S. I just spewed.

              If you were looking for a support group you're barking up the wrong tree. This place is fulla enablers dude. - Shooter77us

              The bitterness of low quality lingers long after the thrill of a low price has gone. - RacerX450

              Comment


                #8
                A few measurements of the springs will enable you to ballpark the spring's rate. As far as the fluid, I always fill measuring with forks collapsed to the top of the fork (usually around 150mm-160mm), never by volume.
                ASMA #139

                Comment


                  #9
                  You'll be fine - just as 6, Parc and Talon says.

                  Do not go by oil volume, you need to control the air volume, so measure oil level... and adjust as necessary.

                  Even if Progressive springs only have one rate listed, it is more interesting what you actually have especially as you got it secondhand. So if you have filled them to a a level, do a testride and see a problem, lots of things can be investigated - but you would need to take everything apart and measure a lot of things.

                  Comment


                    #10
                    I want to thank all of you guys for your suggestions. I have not ridden her yet, but the difference is huge! The fork would like almost BOUNCE before definitely a much slower compression and no more rebound bounce. Still gonna put the last 2.5 oz per leg in. She might yet toughn up some. Oh and I found the preload caps from Partzilla. 92-93 f2 oem $76 each! I found some chinesium ones on Fleabay for $30? Can I use those?

                    Comment


                      #11
                      The Chinesium should be fine as long as you don't mind sending money to China. Pretty hard to avoid these days.
                      Brian - Richland, WA
                      1991 Hawk GT
                      1997 VFR

                      Comment


                        #12
                        Originally Posted by bk94si View Post
                        The Chinesium should be fine as long as you don't mind sending money to China.
                        Or stripping the caps trying to place them on the forks. When it comes to certain suspension and brake components, I suck it up and go OEM if possible.
                        ASMA #139

                        Comment


                          #13
                          Originally Posted by racerboy4 View Post
                          I want to thank all of you guys for your suggestions. I have not ridden her yet, but the difference is huge! The fork would like almost BOUNCE before definitely a much slower compression and no more rebound bounce. Still gonna put the last 2.5 oz per leg in. She might yet toughn up some. Oh and I found the preload caps from Partzilla. 92-93 f2 oem $76 each! I found some chinesium ones on Fleabay for $30? Can I use those?
                          Ive used them before.. They are fine... But if it where me and i was doing t again, id probably go a higher quality route.
                          Don't spend money and buy, spend time and learn.

                          Comment


                            #14
                            Yup silver chinesium ones on the way! Thanks guys!!!

                            Comment


                              #15
                              And like Jan and Bob and everyone said, fluid volume measurement is only to make the air pocket size... isn't even something I measure.

                              I have my notes taken on what my fork setup is, and I don't have how much fluid is in there logged, just the weight and the air gap, the distance from the top of the fluid to the top of the fork.

                              There may be something wrong doing it this way, but whatever it is hasn't impacted me yet.
                              Don't spend money and buy, spend time and learn.

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