A look at a '05 Honda XR650R Cylinder Head

Discussion in 'Thumpers' started by creeper, Sep 24, 2005.

  1. creeper

    creeper Still alive...

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    I recently received a 2005 Honda XR650R cylinder head for inspection and possible repair and improvement... and thought some of our XR owners out there, and maybe others, might be interested in what I've found.

    This head belongs to a gent from Idaho. His concern was that this new bike does not perform like his old bike, so he sent me the head to have a lookie see.

    Here is the head and valve train parts after cleaning, glass beading and cleaning again. After cleaning, I took measurements of valve to guide clearance, valve and seat runout, valve stem protrusion and spring pressure at installed height.

    [​IMG]

    Valve to guide was IN. .001" & EX. .0017".
    Spring pressure was matching within 6%.
    Stem protrusion was within .005" intake for intake and .003" exhaust for exhaust.
    Valve runout was less than .002 max. and averaged .0013".
    Valve seat runout was not so good at and average of .002" for one each intake and exhaust and .0045" for the remaining two... both of which failed a loaded wet test and unloaded light test. So we had a bit of leakage there.
    All the valve seat contact angles were what I felt to be a bit on the wide side, which may have contributed to the leakage.
    Also, one of the intake valves, the one with the better contact seal had a substantial amount of soft carbon deposits on the port side of the valve head, indicating a possible guide seal fault.

    All in all, not too bad.

    The ports themselves look to have pretty effective shapes overall. A little rough, but that’s to be expected in a production head.

    An exhaust port view. Very nice. Both exhaust ports looked like this at the port seat junction, pretty much all the way 'round. Only a small amount of clean-up required here.
    [​IMG]

    And a view up the intake ports. Not so nice. The seat is extending into the port over .050" on the "long side" of the port. That has got to be blended in.
    [​IMG]

    On the short side, a machined surface makes for a less than smooth "short side" of the port. A virtual cliff for the flow to jump off of and become turbulent. A bit of radius work here.
    [​IMG]

    So, that's where we're at. The valves are in nice shape, no serious pitting or cupping and will be reused as per the owner. The springs are fine, as are the guides.
    [​IMG]

    I will be recutting the seats just enough to make them concentric. As the valve faces are in such nice shape, rather than re-machine the faces, I'll lightly lap them in to the fresh cut seats.

    On the ports, I'll be working mostly on the intake side, blending the seats in on the long side of the ports and radius the "cliff" a bit on the short side. I can't make it text book perfect as the casting wall thickness in that area is not real thick to begin with.
    From past experience, I can say that a 4% - 7% intake flow improvement should be realized on the intake side with a negligible loss in velocity.
    I'll buzz out some of the "bigger" lumps in the exhaust ports, mostly because that's what I do... but I doubt there is any room for improvement with out a loss in velocity.

    To be honest, I don't see anything in the head alone that could cause the noticeable differences in throttle response and power the owner is claiming. It's not perfect by any means, but there's nothing really terrible... his previous 2000 XR must have been a real storm trooper.


    I'll post again when I'm close to finished with the head... ciao. :wave

    C
    #1
  2. dagwood

    dagwood Banned

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  3. ChrisC

    ChrisC Amal sex?

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    Chris,

    Please remember when working on Jap heads;

    あまりを取ることの注意深い

    :norton

    CC
    #3
  4. creeper

    creeper Still alive...

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    "Taking remainder it is careful"... roger that. :dunno
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  5. ChrisC

    ChrisC Amal sex?

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    I love these translator engines.....Google says that's "don't take too much off"

    Close enuf :1drink
    #5
  6. creeper

    creeper Still alive...

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    I used World Lingo. We would both be in a world of hurt in Japan.
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  7. ChrisC

    ChrisC Amal sex?

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    Gee, this is fun....

    私の毛深いろばのひびを舐めなさい

    Now back to the cylinder head stuff, OK?
    #7
  8. creeper

    creeper Still alive...

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    :poser :poser :poser... :oscar
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  9. Mack

    Mack Gone, but never forgotten. RIP, Mack...

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    And I actually spent the time to translate that, damn! No fortune cookie there. lol
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  10. creeper

    creeper Still alive...

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    Много удача... меньший cookie.
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  11. aptyp

    aptyp newbie lamer

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    Much luck... smaller cookie. haha three can play at that game. :)
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  12. HighwayChile

    HighwayChile greetings from Wa state

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    i read a ebay post by scott summers selling one of his 650r's , he said the engine was stock except for the head which was custom as a gift from honda, he said it had better low end response, my guess smaller ports?

    I'm not suure if this was a race or practice bike, but he said he did ride it a bunch.
    #12
  13. Max Power

    Max Power Secret Agent

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    [​IMG]

    [​IMG]

    Works of art. :evil
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  14. ponq

    ponq Been here awhile

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    :lurk
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  15. creeper

    creeper Still alive...

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    That would be a good guess. A well designed port doesn't have to have a large cross-section.
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  16. creeper

    creeper Still alive...

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    Well…

    It took a bit longer than anticipated. One of the exhaust seats had more runout than the first inspection indicated and I had to cut about .006″ - .008″ on both seats to get them concentric with matching stem protrusion.
    I don’t like to use thin valve spring shims as they tend to self-distruct… so the trade-off is a slight reduction in spring pressure, but no bits of metal bouncing around inside the engine.

    [​IMG]

    The port work went well; except for some casting flaws just below the seats that I chose to leave rather than take out for purely cosmetic reasons. Removing them would have enlarged the port just before the seat… far too critical an area to increase diameter just so it will look prettier.

    [​IMG]

    [​IMG]

    Reduced the contact seat widths to .045″ on the intake and .055″ on the exhaust… this should provide a good compromise between a long lasting seal and adequate heat dissipation.

    [​IMG]

    Not a “race grade” head by any means, but it should flow well and live a long time.

    Th th th that’s all folks… :wave
    #16
  17. meat popsicle

    meat popsicle Ignostic

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    I hope to ride my bike long enough to need ya to touch my head creeper!
    :rabia

    And for you Mack,

    A little fun: http://www.badcookie.com/

    I did a chinese dinner once and made fortune cookies - easier than I thought. I wrote all the fortunes and borrowed the "Bad Cookie" wisdom. :evil Folks were a bit disturbed, but then once they started reading them aloud, the laughter began. :D

    My personal fav: "Never forget to pillage before you burn."
    :nod :nod :nod
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  18. Max Power

    Max Power Secret Agent

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    Ooooo My.

    I like.
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  19. creeper

    creeper Still alive...

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    Stop masturbating Max... you'll muck up yer' keyboard again. :D
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  20. Mack

    Mack Gone, but never forgotten. RIP, Mack...

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    Very pretty stuff. Almost too nice to put back on the bike, almost....

    Didn't do so good on the fortune cookie: "You will attract uncultured people to your home." think they may be talking about ADVriders??
    #20