Another CRF1000L fork thread!! Reg vs Adv Sport forks.

Discussion in 'Japanese polycylindered adventure bikes' started by Motociclo, Oct 22, 2018.

  1. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Will find a heap if info here on needle size etc.

    https://advrider.com/f/threads/crf1000l-spring-and-valving-data-base.1363798/

    I wouldn't sweat spring rubbing in lower leg.
    Springs are smooth and have plenty of lube.
    If your getting shavings off spring or leg, there is something wrong.
    Even when ano wore in my original tubes, oil was stained but not too bad.
    Idea with bush to sit flush too outer tube is a good idea, but wouldn't over think the spring cause real issues.
  2. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Good idea modding comp needle, but it will bleed a whole lot more than it needs.
    It already bleeds like a stuck pig. Don't want be down on your idea, but it won't improve low speed damping.
    Only 17ml of oil flows through comp adjuster, not real quick either. (Only fluid displaced by damper rod taking up volume.)
    Blunt oem tip doesn't affect flow to be a concern.

    What needle needs is finer adjustment. 12 -14 clicks to coarse.

    Worth a shot changing spring location.
    Bush should always be in oil, even with fork fully extended.
  3. dadouzzu

    dadouzzu Adventurer

    Joined:
    Jan 10, 2020
    Oddometer:
    11
    Location:
    Italy
    Thanks for the link.
    I don't know if the springs can cause problem in this fork.
    In my they did, in 30kkm :( Looking inside the inner tube i can see where every coil was because they scalloped the steel and flaked the chrome. Tomorrow i will try to took a picture.
    From my memory the stock spring are not smooth but shot peened.
    For this reason i prefer to not spry any oil coming from the bottom of fork over the bushing :)
  4. Lost Cartographer

    Lost Cartographer Been here awhile Super Supporter

    Joined:
    Feb 7, 2011
    Oddometer:
    756
    Location:
    AZ and CA
    @dadouzzu

    What cartridges are you using? How do you like them? What diameter are the pistons?

    I was already running the racetech bushing, just added the shim to tighten up the tolerances.

    Without the centering spacers my springs were making all sorts of noise. Adding the lower and middle centering spacers made them nice and quiet.

    I assume that they were buckling and rubbing on the end of inner slider before I added the centering spacers.



    @Motociclo

    My piston bleeds are dramatically smaller than stock - I ran a 0.5mm diameter safety wire thru the 0.7mm bleeds on both the comp and rebound sides.

    My previous valve stack was too soft off road (with comp adjuster full hard) and too firm on road (even with comp adj full soft).

    My latest tuning stack is WAY stiffer in both comp and rebound than the last one. I hope it will be stiff enough off road, and by increasing low speed comp adjustment range I'm hoping that it will be tolerable on road too.


    I'll let you guys know if it works in a month or so.
  5. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    That will help.
    Still the modded needle will bleed a heap.
    Best option is a valve with no bleed and then stock adjuster works well.
    KYB 20mm valve, (YZ85, KX85 etc) or a RT valve. None have bleed.
    Interested how it turns out.

    Its all a compromise.
    You say it valving was to soft off and too hard on, then making it stiffer will only make it feel too hard on road again.
    Get rebound sorted first. To quick rebound will make forks feel to hard and skaty on road.
    What are your springs, weight etc,?
    Happy to help you out with some stacks if you like. PM me if interested.
    Lost Cartographer likes this.
  6. dadouzzu

    dadouzzu Adventurer

    Joined:
    Jan 10, 2020
    Oddometer:
    11
    Location:
    Italy
    I am using Andreani misano 20mm cart.
    Quality and finishing of the components are good.

    Stock valving were quite harsh with a lot of bleed. I have reduced shim stiffness following manufacturer indication and closed the comp from 2 to 3/4 of turn and reb from 2 to 1/2 of turn.
    I have also reduced half step spring rate and lowered oil level from 120 to 140mm.
    Now it feels better :)

    The design is similiar to ohlins nix30 nix22 with only one piston per leg.

    If you put the numbers in restackor you got strange result:

    Due to h.deck the compression piston seems to do add about 300kg at 4/ms even without any shim

    The rebound side start cavitating at about 1,4m/s of comp speed

    Probably is the same with ohlins because the comp has to flow 4x oil and the reb has no base valve to keep up the pressure.

    Maybe it is a restakor fault? Or real word speed are less?
    I dont know...

    P.s. i agree with motociclo, if the low speed rebound is not well damped the fork feel harsh
    Lost Cartographer likes this.
  7. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Restackor is sensitive to input.
    With trying to cover seperate cartridge, set as shock and swap weight dustribution bias.

    Lack of base valve in rebound will have no effect.
    Base valves hardly flow, all work in these cartridges, is in midvalve. A weak base valve will encourage cavitation though. Same as in a shock.

    I would recheck your measurements.
    H deck has effect, but not to that extent.
    Would be guessing it is around 2mm.

    Nthrt can affect output.
    I would set it to "0". These valves are quite open. Stock Showa valves flow enough to set Nthrt to zero.

    It would be unlikely forks are cavitating.
    Hitting a good pot hole will give you 5m/sec of fork speed.
    I tune forks to 5m/sec, shock to 2.5m/sec.
    No issues.

    Happy to have a play with some numbers if you give me measurements etc.
    Lost Cartographer likes this.
  8. dadouzzu

    dadouzzu Adventurer

    Joined:
    Jan 10, 2020
    Oddometer:
    11
    Location:
    Italy
    Thank you Motociclo.
    20190823_012910.jpg
    20190823_012744.jpg
    pistone.png

    For compression:
    H.deck 1mm
    Measured maximum port width 4.3x3mm
    18mm shims
    The dshaft is 20mm because all the oil has to pass throu the valve

    For rebound check valve side
    H.deck 1.5mm
    8x3mm port
    18mm shim
    "Base valve" 4x7mm hole on the side of the tube.
    20mm cart with 10mm shaft

    Ntrht =0

    If you pm me your mail address i can send you the entire restakor file..

    Screenshot_20200112-132138_Dropbox.jpg
    Lost Cartographer likes this.
  9. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Your Drod needs to be 10mm, not 20mm.
    Even though it is a base. Drod is damper rod size, 10mm, not 20mm. 10mm gets used for all Drod numbers in this case. Mid valve and rebound too.
    As far oil flow. Base valve only takes oil displaces by damper rod. With 220mm stroke, 10mm damper rod, approx 17ml gets pushed through.
    The mid valve and rebound see the most oil. Up to 70 ml of oil. It doesn't seem like much. But thats it.

    Hdeck number seems small. You sure its only 1mm.? It looks more than that. Recheck that.

    Don't worry about check valve side, only measure comp side acting directly on comp shims.
  10. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    I have looked in my old lower tubes.
    60k km, no scalloping, flaking chome.
    There are scuff marks where spring rubs, thats it.
    The springs aren't going to be an issue. Only the worn ano if oil isn't changed enough.
    Pic of lower, both the same.
    Left leg,
    20200113_094755.jpg

    Right leg.
    20200113_095027.jpg

    Each they're own, but swapping spring locations and fretting over something that isn't an issue is a bit trivial.
    I know in case if aftermarket cartridge kits, thats how they come.
    This had more to do with lessening unsprung mass, not springs rubbing inside.
    Would rather steel spring rub steel lower than rub alloy upper.
    Get your valving and springs sorted, service suspension regularly, ride and enjoy.
  11. dadouzzu

    dadouzzu Adventurer

    Joined:
    Jan 10, 2020
    Oddometer:
    11
    Location:
    Italy
    The compression valve is not a base valve, is attacched to the damper rod.
    It has to flow 22x2x2x3,14/4 = 69ml.
    You can simulate it with BVc drod=20 or MVc drod=0
    I have recheked few times, hdeck is 1mm :(

    Compression, orange no port restriction, blue hdeck 1mm
    Screenshot_20200112-202633_Dropbox.jpg

    Cavitation on rebound leg:
    Screenshot_20200112-213146_Dropbox.jpg
    Screenshot_20200112-213206_Dropbox.jpg
    Screenshot_20200112-213233_Dropbox.jpg

    I simulated the lower holes of the tube with a check valve with very soft spring

    Maybe there are something else wrong..

    Edit: an example of single piston cart assembly:
    Screenshot_20200113-004748_Dropbox.jpg
  12. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Few things wrong,
    Drod needs to be 10mm on all of the options. BVc, MVc and MVv. Thats what it needs to be.

    Hdeck, 1mm. Ok if thats what it is.

    On first page, midvalve analysis, stroke is at 10mm and 120mm. Needs to be stroke of fork. 220mm.
    Oil height. Seems a bit low.

    I understand in case of comp valve is on damper rod. It is a midvalve.
    But, the base valve is apart of the overall setup and needs to included.
    Where are the shim stacks for midvalve comp and base valve comp?
    Check valves don't come into play either. You seem to using those in pics above, than proper stacks.

    Below are pics of a oem fork cartidges converted to single function per leg.
    Similar set up to aftermarket cartridge kits.


    Study the pages carefully, mistakes and issues your having will be evident.
    If your still having trouble, give me all the relevant info and i will take check ut out.
    You seem ti be struggling with it a bit. I PM'd you.

    20200113_114253.jpg
    20200113_114308.jpg
    20200113_114319.jpg
    20200113_114330.jpg
  13. dadouzzu

    dadouzzu Adventurer

    Joined:
    Jan 10, 2020
    Oddometer:
    11
    Location:
    Italy
    Thanks for the info, but i think we are talking about different type of cartridge :)

    On my (and also on nix22, nix30) comp leg there is no base valve, just a sealed plug, and no hole in the cart. tube (they are up, on the rebound chamber).

    On the reb leg there is no base valve, the oil squirt out freely throu the cart. tube holes.

    20200113_102423.jpg

    Did you ever see or simulated one of this?
  14. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    We are talking about exact same cartridge.
    1 comp leg, 1 rebound leg.
    The comp leg will have a base valve, rebound doesn't.
    Even if comp doesn't have a true base valve, just a plug, we are still talking about same thing. The plug is a base valve of sorts.
    I have simulated these plenty if times.
    What posted earlier is an example of one i have done.
    The holes in the cartridges, at top of comp, bottom of rebound, are just refill/bleed ports and offer nothing to damping.
    I can see how you think these cartridges work, but it isn't like you think.

    Take the base valve out so it is something closer to what you have, this is how info needs to be entered to get meaningful results.

    Just trying to point you in right direction.
    I can see the mistakes your making and why your out put info isn't right.
    Just trying to help.
  15. dadouzzu

    dadouzzu Adventurer

    Joined:
    Jan 10, 2020
    Oddometer:
    11
    Location:
    Italy
    Ok, i very apreciating your help.
    This evening i will update the stroke parameter.

    I'm just trying to understand.

    On std damper (with sealed upper chamber) the midvalve oil flow is:
    Dvalve - Drod swept volume
    (22×2×2×3,14/4)-(22×1×1×3,14/4) = 69 -17 = 52cc

    On this damper with sealed bottom the flow is:
    Dvalve swept volume
    22x2x2x3,14/4 = 69cc

    Did you agree? How do you simulate this?
    You set drod to 0?

    On rebound leg the only compression pressure drop is on the midvalve that in this damper is a check valve with 0.017kg/mm spring.

    If the pressure drop became more than 1 bar it start to cavitate. Is correct?

    Thank you
  16. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Don't worry about the flow. It is relevant, but not important at this time. The oil flow through valve is in the data, but represented as L/min from memory. Like i said, not important at this time.

    Drod is 10mm. Thats it. It is 10mm in all of the pages. BVc, MVc, MVr. Look at the info i posted again. You need to set Drod to 10mm.

    Dvalve is just the piston. 20mm.

    The check valve doesn't come into play on rebound stack for compression. Don't worry it either. It simply opens so rebound chamber can fill.

    Cavitation caused by too greater pressure drop on rebound side of comp midvalve.
    Pressure it starts at. Not sure, guessing 0 bar.

    To be fair, i think your getting ahead of your self worrying about fliw etc.
    Get the right input data in the right places.
    I believe you won't see the cavitation in the results your getting.
    PM me your shim stacks, spring rates, your weight and i will try and make some sense of it for you.
  17. Gman73

    Gman73 n00b

    Joined:
    Dec 19, 2016
    Oddometer:
    2
    Motociclo! You are a King among men!!! You should receive a Sainthood for all your contributions. I’ve been reading all your posts obsessively lately, thanks SO MUCH for sharing all of this knowledge. I’ve learned so many important things to know about these Showas as a person who plans to own them for some time to come. You are awesome!
  18. Motociclo

    Motociclo Long timer

    Joined:
    May 18, 2017
    Oddometer:
    1,153
    Location:
    .
    Happy to help.
    Your words are very kind.
  19. NSFW

    NSFW basecamp4adv Super Supporter

    Joined:
    Feb 20, 2007
    Oddometer:
    25,959
    Location:
    Burbank CA
    really appreciate your excellent work, i'm glad to find this and will use it as my guide to address my current situation. going to put atas uppers. thank you Motociclo and great to have you in the community.

    maybe i don't need the atas lowers since i'm going to lower the front by an inch which will shorten the stroke and put the bushings/sliders higher in the upper tube.