tires, fork oil, road, old tech? Whats causing my bouncing front forks

Discussion in 'Airheads' started by mfp4073, May 21, 2012.

  1. batoutoflahonda

    batoutoflahonda Long timer

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    Unfortunately, fork oil doesn't really have a standard. Bell ray's 6.5 maybe Gloden Spector's 8.0

    You want quick and simple? Go down to the BMW shop and get what's recommended for your bike. Or, you take my word, a guy you never met, and use Mobile 1 synthetic ATF. That's what I use. I like it. And I'm known as an upstanding pillar of society.
    #21
  2. mykill

    mykill odd

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    My money is on this for being a culprit.
    #22
  3. mfp4073

    mfp4073 Long timer

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    Ok, still been doing my reading and researching. Currently looking for an easy to find local source for fluid (not prepared to use ATF at this time due to some of what I have read.

    Local napa has this:

    [​IMG]

    whatdayathink?

    about the ATF, have seen mention that ATF has friction modifiers in it.

    http://www.advrider.com/forums/showthread.php?t=452366


    Have also seen mention of aviation 5606

    http://www.bmwmotorcycletech.info/miscl.htm

    I have access to all the free 5606 that I want from the aviation work I do. My understanding is 5606 is basically mineral oil and paraffin wax.
    #23
  4. supershaft

    supershaft because I can

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    IMO experimenting with oil in the middle of problems is not the solution. Get some Spectro 5wt fork oil if your bike is a 70's model I believe?
    #24
  5. mfp4073

    mfp4073 Long timer

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    I had thought in my reading that the fork oil was supposed to be a 7.5 weight according to the BMW spec, but now dont remember where I read that. I dont have a supplier for any of the oils listed in the hayens manual yet. Still searching (all bmw dealers are over an hour away from me)
    #25
  6. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    So you've found a hydraulic oil at NAPA that is "suitable for cold climates" and you are in... Florida.

    Spectro 5wt is the ticket.


    ^^^oops, was thinking BelRay amd wrote Spectro. Same diff, tho.
    #26
  7. supershaft

    supershaft because I can

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    They started out recommending 2.5 weight and went up to 7.5. IMO they work best with 5wt unless you ride real hard. Spectro that is. Call up your local bike shops or mail order it from any number of places.
    #27
  8. squish

    squish Out of the office.

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    First thing I'd do is make sure that everything suspension related front and rear is working
    Make sure the forks are straight and true, that the wheel is in fact round and the bearings are in good shape.
    Then check swingarm pivots and shock bushings. and rear wheel.
    Tweaked fork tubes or bent axles can jack up the way a fork works.

    Then go about draining and refiling the fork oil. I lean more toward's what Shafti was saying rather then duane.

    Also use fork oil rather then ATF, when these bikes were new ATF was used a lot as there just wasn't really that much for oil around. Now there is, and now it's good stuff.
    Trouble is what's 5 weight from one brand is 2 weight from another and still 8 from someone else.
    So when trying to find the right weight use the same brand. I've used and have been happy with both Spectro and Honda Pro Oils.

    I start out with a thinner oil and work my way to a thicker oil if needed.
    #28
  9. mfp4073

    mfp4073 Long timer

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    Ok good news, the cycle gear across town has the belray in 5,10, and 15 weight. So thats under control. Need to find a measuring device and make a tool to loosen then fork caps next. (recovered my seat this weekend, so not wasting time!)
    #29
  10. batoutoflahonda

    batoutoflahonda Long timer

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    The only time I've ever rubbed ATF between my fingers is when I was trying to get it out of my hair. Usually after lying under some four wheeled contraption. Not a fair experiment tho, as I'm sure ATF doesn't contain sticks and rocks. Well, maybe some of the GM stuff does.

    Nice that you have a store that has the same brand with varying weights. Now you can do some real trials. Good luck.
    #30
  11. GodOmelet

    GodOmelet Adventurer

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    I just did my fork oil on my 77 R100/7 last weekend and used the recommended 7.5wt BMW stuff.
    The old fluid was hesitant to come out until I employed Duane's method of tapping on the fork brace w a rubber mallet until the lowers drop (obviously after taking off the lower caps and nuts/washers and loosening the filler caps). Put something below to catch/support the forks when they drop. The fluid comes out in a big gush. Then I used a little jack to carefully raise the fork lowers back up and thread the rods with the locknuts. My local mom
    and pop pharmacy had a 60ml syringe for a couple of bucks that worked a trick on refilling. She's riding much smoother now.
    #31
  12. mfp4073

    mfp4073 Long timer

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    Update:

    Finally did my fork oil yesterday. Glad I had both the haynes manual and the clymers. It was not said in the haynes manual that once the bottom nut is off that you have to push up on the shaft. One side wouldnt drain and it was only upon reading the clymers that it made more sense. Also, I was suprised that there was not an inner "cap" and the outer cap was the actual seal. It appears that someone used a pipe wrench to take them off once before! :huh

    Anyway, the left side was water fouled (discolored). Both sides were pretty nasty though. No big chunks or anything in the fluid. Filled and plunged as the instructions say. Today made my ride to work and seems like the sticktion I was getting is completely gone. With that the dampening effect that the front forks are supposed to do seems to be working much better.

    My plan is to run it a week and do another fluid change and replace the gaskets on the caps.
    #32