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New valve parts not fitting like the old ones

Discussion in 'The Garage' started by desertrider, Aug 25, 2015.

  1. desertrider

    desertrider XS650 Member

    Hi - I am putting my top end back together. I sent the head out to a good shop and had a valve job etc. done. Old intake valves were not good, so the shop bought 2 new valves (from Mikesxs, I believe) and returned parts to me. I bought a new spring/cap set from Mikesxs.
    Now I am assembling the head, and have noticed that the new combo of valve, keepers, and cap result in the top of the valve being flush with the spring cap - not good.
    I measured some combinations and found the top of the valve to protrude ABOVE the spring cap by this amount:
    old cap, keepers,intake valve: + .040
    old cap, keepers, new intake valve: +.040
    old cap, new keepers, new intake valve: +.020
    new cap, keeper, old valve: +.040
    new cap, keepers, intake valve: FLUSH

    The cap IDs are:
    old: .162
    new: .168

    After looking this over, it seems the valve is the variable that causes the problem.

    Any experience with this?
    Suggestions to make the new valves (already ground to fit head) work?

    Thank you!

    Attached Files:

    Last edited: Aug 25, 2015
  2. desertrider

    desertrider XS650 Member

    also - old/new valve shaft diameters are the same - .315.
  3. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Good catch, desertrider.

    Probably wouldn't have this if using genuine factory parts.

    But, as long as the tip of the valve is above the keepers, shouldn't be a problem. The stock valve adjuster motion will stay within the area of the valve tip. Else, with elephants foot adjusters, there'd be a problem. You can view the valve/adjuster geometry here:


    More valve issues:


    MikesXS offers a performance valve spring package that has a seriously deep pocket in the top retainer, which allows for a little more valve lift before spring bind. Unusual and terrifying to behold, the valve tip is below the retainer, but I guess they work ok. Somewhere in here is a picture, but I can't find it...
  4. desertrider

    desertrider XS650 Member

    Thanks you for the reply Twomanyxs1bs- a lot of good information here! I'll take some time and read through it.
    I was mostly concerned with running out of adjustment down the road - .040 seems like a lot of difference, but maybe not a problem. Are there any good aftermarket adjusters (cap screw and nut)?
  5. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The adjustment geometry is dependant on the fitted valve length, from valve seat/face to stem tip.
    The height of the springs and retainer are independant of, and don't affect, this final stem tip height.

    Members here have used alternate valve adjuster screws, 8mm-1.0 threads, factory versions from VW/Porsche and Yamaha Virago...
  6. desertrider

    desertrider XS650 Member

    Yes - understand. I'll search about other valve adjusters and see what I can find. Thank you.

    Would you have any concerns about the intake and exhaust springs being compressed to different values? Both intake would be the same and both exhaust would be the same, but in/out would be different by about .040". I'll measure later tonight to get exact number.

    Question is, what is the correct compression value for best performance? Seems I can't change the compression amount (guess I could shim the exhaust to match intake), so maybe I shouldn't worry about it. Am I overthinking this? haha
  7. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    No, you're not overthinking it. You just have more questions than answers.

    Doing mechanic's work with factory stock parts and normally worn engines is one thing. Drop in and go.

    Trying to fit questionable quality/tolerance aftermarket parts to old/worn/neglected/abused machines with dubious histories, takes a bit more engineering. A different world. Quite challenging even for the mechanics.

    So, keep doing your research. Valve spring lengths, compressed heights, and shim options, are your next step. Here's an excerpt from the manual.

    Attached Files:

  8. desertrider

    desertrider XS650 Member

    awww - more homework? haha thank you, this is a big help.
  9. desertrider

    desertrider XS650 Member

    So I have worked on this and have installed all four valves with the same top profile. All are about flush with the caps.
    I have made an indirect measurement of the compressed spring lengths and am satisfied that they are within a few mils of spec (1.457). The inner spring is compressed more, due to the taller cap profile for the inner spring. Nothing I can do about that, just guessing that the spring has a different k and force would be equivalent.
    I'm going to leave the valve adjustment screws as-is, maybe upgrade later when it's running.
    Thanks toomanyxs1bs for your help here!

    Now onto top end assembly!
  10. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Good deal, desertrider.
    Love it when new members can grasp and apply their new knowledge.
    Let us know how it goes...

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