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Mailman’s XS2 a full on restoration

Discussion in 'The Garage' started by Mailman, Mar 1, 2018.

  1. Mailman

    Mailman Hardly a Guru Top Contributor

    Those are made by ARS, I bought them as part of a complete set On eBay. Unfortunately the set came with two of the same rotation specific cam seals. I never used them, I ordered a set of OEM.
    arcticXS and Jim like this.
  2. arcticXS

    arcticXS XS650 Guru Top Contributor

    It seems reasonable that the "R" after the dimension numbers indicate CW rotation. So maybe someone should try to locate an "L" version for CCW?
    Mailman likes this.
  3. Rasputin

    Rasputin XS650 Addict

    709FC534-58BA-4113-9B8A-D0007B1B3793.png This could be the answer. Installed during rebuild, one bearing either side with the inner seal removed.
    JAX71224, Jim, Mailman and 2 others like this.
  4. Paul Sutton

    Paul Sutton Buckhorns on XV1000SE Top Contributor

    Could you just push the seal in backwards??
    Jim, Mailman and MaxPete like this.
  5. Ozboy

    Ozboy XS650 Addict

    I removed my lip and it is tricky to do up aginst the bearing, kinda peeling tearing away. I dremeled three cut marks into the breaking away ridge. Small amount of BLUE loctite hit it home and done. Thinking on that, leaving the breakaway ring on the sleeve up against or just off the bearing will be fine. I am sure oil will get slung on the seal.
    Jim, Mailman, Paul Sutton and 3 others like this.
  6. kshansen

    kshansen XS650 Junkie Top Contributor

    Interesting, wonder about the reason Yamaha felt the need to use two thin bearings in that application?

    Also gets me thinking about why they didn't run a ball bearing at one end and a roller bearing at the other to allow for difference in expansion from heat of the aluminum head and iron/steel of the camshaft.
  7. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    To keep the profile of the head down I suspect.
    Last edited: Apr 14, 2020
    Greyandridin and Mailman like this.
  8. arcticXS

    arcticXS XS650 Guru Top Contributor

    I googled a bit, and found some really good info on seals from Koyo, who also make ball bearings and other bike and car components.
    Koyo actually have 3 types of seals with "pumping ribs":
    Koyo Helix and Koyo Super Helix are the two with a defined direction of rotation. The part ID is as follows, for both:
    MHSA xx-xx-xx XRT or XLT. The xx are the dimensions of the seal. XRT and XLT are indicators of direction of rotation.
    In the PDF I downloaded, there was also some good info on shaft dimension tolerances, surface finish, shaft end bevels, and material properties. All interesting reading and possibly helpful when trying to find the underlying cause of leaking seals.
    Last edited: Apr 14, 2020
  9. MaxPete

    MaxPete Lucille, Betty & Demi - I suggest but THEY decide. XS650.com Supporter Top Contributor

    Yup - agreed. When you design a bearing installation, there are several factors to be considered:
    • radial and axial load carrying capacity (axial loading isn't much of a consideration here but the radial loads imposed by the timing chain tension and the rocker arms does represent a fairly strenuous fatigue situation)
    • mounting conditions (how rigid are the pockets into which the bearing(s) will be pressed)
    • load & support conditions (how likely is the shaft to deflect under load)
    • available lubrication (should be pretty good inside an engine)
    • operating conditions (temperature, vibration ;), shock loading - like from valve actuation, any contaminants in the oil etc.)
    • expected life (in revolutions - which in an engine would be very high)
    • available installation envelope (i.e. how big a spot you have to fit the bearings in and how can they be installed and removed for replacement)
    • cost (always a consideration in every engineering problem)
    ....and there must have been some combination of factors that drove them to the slightly unusual and relatively complex arrangement that they chose for the XS650 engine.

    The loading conditions of the XS650 camshaft are fairly severe because there is a fairly significant load in the centre (the timing chain tension) with no supporting bearing. There are also loads along the length of the shaft which vary quite a bit each rotating cycle - the rocker arms loads. This means that the shaft will flex a fair bit and this means that the end-mounted bearings will have to absorb some angular deflections during each rotation.

    NOTE: in considering the expected or required life of the bearings in an engine like an XS650, at an average speed of 40 MPH for a life of 50,000 miles, the camshaft will turn more than 112 million revolutions - if you assume an average engine speed of 3,000 RPM - and the crankshaft will turn exactly twice as many revs - more than 225 million revolutions - just under a quarter of a billion revs.
    Last edited: Apr 14, 2020
  10. Mailman

    Mailman Hardly a Guru Top Contributor

    Just a side note on ARS ( Arai Rubber Seal ) company. They were founded in Japan in the early 50’s and both Yamaha and Honda used them extensively in both their factory race bikes ( and in Honda’s case also race cars ) and in their street bikes. Toyota has also used them in their cars. They have since opened factories in several Asian countries.
  11. MaxPete

    MaxPete Lucille, Betty & Demi - I suggest but THEY decide. XS650.com Supporter Top Contributor

    I wonder if they have become the well-regarded helmet manufacturer?
    Greyandridin likes this.
  12. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Mailman, MaxPete and Greyandridin like this.
  13. arcticXS

    arcticXS XS650 Guru Top Contributor

    Here is the website where I found the info on oil seals. Scroll down a bit for downloading of the oil seal/ o ring PDF document.
    There are some "small talk" sections spread through the document, with various issues highlighted. One of them is regarding shaft surface finish, where sometimes spiral shaped micro grooves can cause a leak, by transporting oil past the seal. They specifically recommend "plange (plunge?) cut grinding" and discourage "paper lapping". This was all new to me, as I easily could be tempted to "clean up" a shaft sealing surface with Schotchbrite or fine emery cloth. You learn something new every day :)
    TwoManyXS1Bs, Mailman and MaxPete like this.
  14. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Justa quickie blurb on the cam bearings and seal leakage.

    The cam bearings are spec'd as the looser C3 clearance, presumably to tolerate gritty oil.

    The engine crankcase pressures pulsate, enuff to challenge any oil seals.
    Hence 5twins' recommendations for 1-way reed vent valving...
    MaxPete, Mailman and GLJ like this.
  15. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    I have a couple of XS1 cams that I need to rework, *someday*.
    Was contemplating a simple lathe project to renew the oilseal grooved cam ends.

    XS650-CamshaftEnd-01.jpg XS650-CamshaftEnd-06.jpg

    There's enuff meat and room there to steadyrest the end, and turn down about 0.015" - 0.020" of the outer 1/2".


    One end has a keyway slot, making steadyresting a challenge.


    Could slide a single bearing on there, clamp it in the steadyrest fingers.
    Still enuff room to get a cutting bit in there.

    After turning this shoulder, fit and bond a sleeve onto the end. Doesn't need to be a press fit, doesn't need to be accurate, just bond an oversize sleeve on there. It's not a load bearing area.

    After bond cure, turn it down to match the original 25mm. That way the original cam bearing installation procedure is unimpeded.

    Also, the original cam ends have an overly generous edge bevel, which robs the cam seal of precious contact width.


    After the final sleeve turning and end-facing, only a gentle rounding of the end edge need be done, making the end full-length, giving the seal more purchase.

    Too much on my plate for this now.
    Whut say you, lathe guyz?
  16. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Dangit, another double-post...
    Last edited: Apr 24, 2020
    MaxPete likes this.
  17. Mailman

    Mailman Hardly a Guru Top Contributor

    Those are some interesting ideas. I also noticed that bevel on the end of the cam. I’ve got a couple photos that shows the seal , right at the edge of that bevel.
    DBE69179-7D24-4360-B1E3-CC3F241CAF57.jpeg 607B1305-BCA8-4282-B969-2CA6B354CE4F.jpeg
    TwoManyXS1Bs and MaxPete like this.
  18. yamahama

    yamahama XS650 Enthusiast

    Lol, wow, just read the 1st page of this whole thread...but will continue as I am a month into the search all over the place for same bike and just found a 20ish k mi. cleaner upper original 10 mi. from my house.. Belongs to a collector who has (soon to had two '72's). Dirty, missing turn signals,brake lens broke, rear brake switch missing.Otherwise all original no dents in tank, sides but some small splotches on nice original tank in n out. Old cracked Dunlop gold seal F7 tires...they hold air! I am really jacked over this pending project. Even though the engine have proper level, clean oil and engine looks not to have been apart...it's coming apart...probably to be on the safe side.....OK, I'll finish reading this tread...and forget about chasing a more expensive somewhat done bike.
    GLJ likes this.
  19. Mailman

    Mailman Hardly a Guru Top Contributor

    Haha! Good luck with your build. I can’t wait to see some photos when you get going.
    gggGary likes this.
  20. yamahama

    yamahama XS650 Enthusiast

    I think I got sidetracked on this thread looking for info re: early xs seat originality using gold vs white "YAMAHA" script on rear of seats. Glad I got sidetracked.
    gggGary and Mailman like this.

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