Fork subtanks... are they for you?

Discussion in 'Thumpers' started by creeper, Aug 27, 2006.

  1. motometal

    motometal i like motorcycles

    Joined:
    Aug 19, 2007
    Oddometer:
    4,292
    Location:
    Baja, Motorcycle Heaven
    the next step would be mini servo controlled valves with a fuzzy logic controller tied into the gps
  2. tirebiter

    tirebiter Been here awhile

    Joined:
    May 8, 2004
    Oddometer:
    499
    Installed my kit today.
    No problems, took less than a 1/2 hour total. Swung the bars lock to lock to make sure the clamps didn't hit anything, and I still could access the bleeders & control valves.

    [​IMG]

    The number plate fits just fine, and protects the valves.
    [​IMG]

    Everything fit super sano.

    [​IMG]

    ..Gonna burn some Turkey off Friday, see if it works.
  3. mrbing73

    mrbing73 bOOb

    Joined:
    Jun 21, 2007
    Oddometer:
    9
    Location:
    Burnt River, ON
    Sounds like just the thing for my DR.

    Looking outside it might be awhile before my ride report though. Say March 08. :cry
  4. GSteve

    GSteve Long timer Supporter

    Joined:
    Feb 26, 2003
    Oddometer:
    2,033
    Location:
    Sandy, UT
    After reading about some of the modifications bmwktmbill had done to his 640 Adventure I thought that I could make similar changes and a short old guy could find happiness with a reasonable weight off road long distance travel machine. So a couple of months ago I lucked into a very well setup 640 Adventure in Salt Lake City. One of the more fortunate parts of this tale is that Zerodog is also located in Salt Lake City.

    Before making an offer on the bike, I called Rob and discussed lowering the LC4 and modifying the suspension for my style riding, my weight and the load I usually carry. Rob even offered to take a look at the Adventure for me. What a guy!

    Needless to say, I bought the bike. Rob picked up the bike for me and began transforming it with new springs in the forks, re-valving and his sub tanks. He also rebuilt the shock and replaced the rear spring with a new custom sized spring. The end result was a bike that’s about 2.5 inches shorter without resorting to links.

    Shipping the bike to Virginia turned into another odyssey, but I won’t bore everyone with the details. The lowered bike, with my 30 inch inseam, makes things very nice, even with a standard height Renazco seat. Combine the lower weight (200 lbs less than my R1200 GS Adventure), narrow width and reasonable seat height should make for a great back roads travel bike. The installation was neatly done and Rob was helpful, professional and patient, even dealing with the shipping companies unexpected demands.

    In any case, I finally got to take the 640 for a ride today. All I can say is, AWESOME!
    Now given that I’m not a great off road rider. I‘m not a Baja racer for sure. However, I do have some long distance gravel road experience with both the 1150 and 1200 GS Adventure bikes. Compared to those behemoths, this thing with this suspension, rocks.

    Today I was able to ride wet muddy roads with potholes while sitting and didn’t get jarred and always felt hooked up. Even when I rode the BMWs while standing, they never felt this secure and they had new or near new tires on them. This particular 640 Adventure has a pair of Saharas that have perhaps 1500 miles left in them. This particular test session was conducted with the valves open and the sub tanks in operation.

    With the valves closed, the road suspension felt taut without any hobby horse nose dive when braking. I still need to spend more time getting used to the bike before I really step it up, both on pavement and gravel. So far, I’m more than impressed and ready for the weather to let up so that I can further the explore the limits of this setup.
  5. Zerodog

    Zerodog Long timer

    Joined:
    Jun 9, 2006
    Oddometer:
    1,233
    Location:
    SLC, UT
    Thanks for the write up GSteve I'm glad to hear you like it so much. I can't wait to hear about it when you get to do some more offroad and try riding with all of your gear.

    Tire biter, post back when you get to ride that sweet ass KTM. Good job on the install!
  6. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,988
    Location:
    Traveler
    Hiya GSteve,
    Ain't it so good it hurts.
    There is just something about the lowered KTM that is magic.
    And how about those sub tanks??!!

    My alternate rear shock is with Rob now getting the GSteve treatment so I can go "linkless" too. It has been a battle but I think we are getting our thumpers daled in!!.

    One last suggestion is the Scotts Steering stabilizer if you don't have it.
    It too is a revalation unlike anything I ever experienced on a motorcycle.

    [​IMG]


    I wish Rob was a Scotts dealer.
    BTW I am short and old also.
    b.
  7. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,988
    Location:
    Traveler
    A better picture...

    [​IMG].
    b.
  8. GSteve

    GSteve Long timer Supporter

    Joined:
    Feb 26, 2003
    Oddometer:
    2,033
    Location:
    Sandy, UT
    Bill.
    Yep, so far it's been great and I don't expect that to change. I just wish the weather would. In any case, I already have the Scott's, only the under bar set-up. As a result, I need to have a longer decompression release cable built or try some other routing scheme. I'll try to get some photos posted later this weekend. What tires did you settle on?
  9. Zerodog

    Zerodog Long timer

    Joined:
    Jun 9, 2006
    Oddometer:
    1,233
    Location:
    SLC, UT
    I don't really like steering dampers. They feel weird to me. Kind of like a flat front tire. Especially going slow. But I think they would be nice on the highway and on rutted sand. Lots of guys like them.

    GSteve I turned your damper all the way off or all the way fast. I don't know if you messed with it yet.
  10. GSteve

    GSteve Long timer Supporter

    Joined:
    Feb 26, 2003
    Oddometer:
    2,033
    Location:
    Sandy, UT
    The new ('06) ride.

    [​IMG]

    Zerdog's little gems in place. Nice install.

    [​IMG]

    A little closer look. The blue knob is the valve the opens the sub tanks or not. The knob is in the closed position for street riding. In other words the tanks are OUT of the system with this setting.

    [​IMG]

    The Scott's damper and GPS set-up. I need to spend some more time with the current GPS configuration to tell if I want to keep it this way or move it further forward on a road book holder or by some other means. Old eyes would probably prefer it to be a little further away.

    [​IMG]
  11. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,988
    Location:
    Traveler
    Hi Steve and Z dog,
    Well maybe steering dampers are not for everone but for me the feeling of security is priceless. I run mine pretty darn tight in bad sand or slippery conditions.
    My reflexes are old.
    Several times at speed I know the thing saved me when thre bike started hopping side to side and threatened to crash.

    For tires for me if I have to slab a few thousand I use Kenda 270, otherwise Mezler Karoo's or MT 21's.
    The differences between these tires and the Sahara"s was night and day off road.
    b.
  12. tirebiter

    tirebiter Been here awhile

    Joined:
    May 8, 2004
    Oddometer:
    499
    The first time I rode with the tanks I was pogosticking all over the place, so I took your advice and added about 15mm more oil & turned the compression in 3 clicks- bingo! Smooth as silk now. :clap

    I liked the tanks so much, I went out to the garage & bodged a set together for my 300. Made them slimmer, but still 75cc in volume.
    Hope you don't mind...:wink:

    [​IMG]
  13. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,988
    Location:
    Traveler
    Tirebiter,
    Really nice...sould be on the Russian Mars lander.
    b.
  14. tirebiter

    tirebiter Been here awhile

    Joined:
    May 8, 2004
    Oddometer:
    499
    Hey it's a dirtbike, not some over-farkled out pavement pig.

    Usually comes home lookin' like this..

    [​IMG]
  15. jgas

    jgas Stoogely Adventurerer

    Joined:
    Nov 7, 2006
    Oddometer:
    843
    I hated steering dampers until I bought a WER and set it like I wanted. Riding bikes with dampers set up for others is not a good comparison. YOu have to set it for your style and preference. In one afternoon I was able to go 10% faster on my 04 KTM 250 exc in the rough stuff. Some bikes need one more than others. To me, lighter bikes need them more, as well as bikes with a steep steering rake. Waste of money on a KLR 650.

    www.ktmtalk has tips on how to make your own subtanks for cheap. You can use your handlebars as subtanks, plastic hose in a coil, or make your own out of PVC. They do work. No doubt about it. Also on ktmtalk there is a bike dealer in some state that sells their own subtanks for 150 a set, and they get very good reviews from customers. I looked for the thread, didn't find it, but it's there somewhere.
  16. Nicolasleon

    Nicolasleon Gnarly F5er

    Joined:
    Aug 27, 2009
    Oddometer:
    225
    Location:
    Chile - currently in Brisbane
    It would be nice that the air tanks included with a high pressure valve to put some extra pressure into the system when being fully extended in order to get a stiffer but not that progressive suspension.

    If im not clear enough, imagin a force curve, which is somewhat linear (to make things simple) when using the subtanks open and more like a leaned J when using them closed. Now; if we add pressure to the initial system we can move those curves higher up in the force axis without compromising the shape of the curve.

    This solution is cheap and easy, and adds another type of important regulation.

    In the MTB downhill competition world suspensions are THE most important issue. I rode for 3 years a fork with air cartridge, no coils; and having that kind of preload regulation can be very usefull for different terrains!
  17. Zerodog

    Zerodog Long timer

    Joined:
    Jun 9, 2006
    Oddometer:
    1,233
    Location:
    SLC, UT
    The DH forks are a different deal. The airspring chamber is longer, sealed from the main oil chamber and designed to work as the main spring. On a motorcycle fork the coil spring does most of the work. The air spring provides progression in the system. In general excess air pressure is a bad thing and you loose small bump sensitivity. This is why bleeding the pressure off of forks is really important. Products like speed bleeders are very popular for this reason. The subtanks I build have the bleeders built into the system. If air is needed to hold the bike up in the stroke or prevent bottoming you have the wrong coil springs for your weight and riding habits.
  18. Nicolasleon

    Nicolasleon Gnarly F5er

    Joined:
    Aug 27, 2009
    Oddometer:
    225
    Location:
    Chile - currently in Brisbane
    Could you give us or PM me the link in ktmtalk?
    thanks mate!
  19. WayneC

    WayneC Long timer

    Joined:
    Oct 3, 2008
    Oddometer:
    5,077
    Location:
    Sydney, Australia
    A bump on this fine old thread to see if zerodog could cast some light on the check valves being used out there now on some subtanks which allow adjustment of compression air flow and fast release of rebound airflow.
  20. meat popsicle

    meat popsicle Ignostic

    Joined:
    Feb 9, 2004
    Oddometer:
    14,586
    Location:
    Circumlocution Office of Little Dorrit
    I don't speak for zerodog, but fine adjustments would be lost on most of us FFs. Sure racers will notice, but after a few years of using his subtanks, with a revalved/resprung WP suspension (real suspension fluids too! :lol3), I can safely say that ON/OFF is plenty of adjustment for an ADV-type rider.

    Creeper said as much in his review thread, but maybe you are referring to something else? :beer