HKO head casting numbers.

Discussion in 'Concours Section' started by Tripod, Jan 24, 2020.

  1. Tripod

    Tripod Active Member

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    I finally tore down my HK0 motor that i hasnt run since 2013. I literally bought it, drove home, took it up and down the street once, then put it in storage.

    It has a stripped out spark plug hole in the head. REALLY stripped out. I can pull the plug out by hand. Im not quite sure i want to invenst in a helicoil for the head and heres why:

    The head has no casting marks on by the fins above the cam cover. There isnt a flat spot wide enough. On the top fin above the spark plug hole there is an "L". On the bottom of those fins is "M4". I think this may be a C70 head. The motor had a 72cc jug and piston.

    What casting number should i be looking for on a HK0 build date 6/70 vin 119xxx?
     

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    #1 Tripod, Jan 24, 2020
    Last edited: Jan 24, 2020
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  3. allenp42

    allenp42 Well-Known Member

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    I have a HKO with a build date of 12/70, and it has "e10" cast in the head. I feel sure this is the one it was born with.

    I once had a HK0 with a build date of 11/70 and it had an "e9" head. Would not wager a bet on this one.

    Maybe someone will chime in with info a little closer to your build date.
     
  4. Gary

    Gary Well-Known Member

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    It will take me a couple of days to check my head markings,I think it is blank but not sure at all. Engine number CT70HE 142836 from bike 142894 built 11-70
     
  5. Tripod

    Tripod Active Member

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    Thanks for the info guys.

    Gary please post up what you find.
     
  6. Gary

    Gary Well-Known Member

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    I'm not near the bike so had my son go take a picture. Turns out my thoughts were wrong it is an E9. Don't be confused by the cylinder markings it's an older CHP 85 kit



    Resized_20200126_104045.jpeg
     
  7. Tripod

    Tripod Active Member

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    I looked at some of the hk0, hk1, xl, sl, and cl70's in Pohlson's enthusiast guide. Now im starting to second guess myself as some of those bikes have the same cylinder head. Im wondering if the 4 speed engines were assembled at a different plant and or in batches.

    Gary, im not saying yours isnt originaljust that it may be a possibility that some motors didnt have a casting number in the usual spot.
     
  8. racerx

    racerx Administrator
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    We've seen a lot of weirdness with cast markings, over the years. I'll add one more possibility...a service replacement head, or head casting. It's doubtful that Honda gave a damn about casting numbers outside of the production line and then only to track inventory, or potential defects. As unlikely as it may be, it is possible that a head could have been replaced by the dealership, or before it was shipped to the dealer, due to damage or a defect.

    Aside from the markings, I see nothing unusual about this head casting.
     
  9. Gary

    Gary Well-Known Member

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    And I don't really have any idea either,I can only assume. I bought it back in '03 on ebay the bike it was from was being completely parted out. Looking back I think I should have bought the frame too....
     
  10. Tripod

    Tripod Active Member

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    Ill get better pictures tomorrow.
     
  11. racerx

    racerx Administrator
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    Just dawned on me...If this is your '79 then it's no wonder the casting marks are a mystery. Just aren't many of them around.
     
  12. kirrbby

    kirrbby Well-Known Member

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    I don't think that's a CT70 head. Pretty sure it's from a different bike. Not sure what tho...CL XL maybe. I can't remember. I'd look around eBay for a similar head, and I'd start by looking for CL and XL heads.
     
  13. Tripod

    Tripod Active Member

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    No this is from my '70 HKO.
     
  14. racerx

    racerx Administrator
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    In that case..."mystery resumed".

    This looks like a usable head. But, if casting numbers/markings matter to you, then sourcing a known K0 casting makes more sense than just rebuilding this one.
     
  15. Tripod

    Tripod Active Member

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    Here is some better pictures .
     

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  16. darrel gunderson

    darrel gunderson Active Member

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    Looks like SL or XL head. Need to see the other sides of it though.
     
  17. OLD CT

    OLD CT Well-Known Member

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    Looks like the valves have lead deposits on them from the leaded gas era, so it's most likely been on that engine a long time.
     
  18. Tripod

    Tripod Active Member

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    I noticed the scale on the valves after i cleaned the head a bit. Didnt know that's what it was. I just figured rust and carbon.

    I remember leaded gas at around 0.89c a gallon in 1983. I think. Long time ago.
     
  19. OLD CT

    OLD CT Well-Known Member

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    Yep, I remember 99 cents in 1984. I had a 1970 Mav that burned it. Think it was around 89 octane for regular. It went bye bye soon after. It resembles ''concrete'' when removing the buildup.
     
  20. 4-gear

    4-gear Member

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    I have various years and models of ct70, xl70 and sl70 around here. Ko, hko, hk1, k3 and all years xl and sl. Have an 85 atc70 also. So if I can be of any assistance, just say the word.
     
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  21. kirrbby

    kirrbby Well-Known Member

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    Here ya go. XL70 #1004362
    L M4

    IMG_20200129_172952000.jpg IMG_20200129_173002676.jpg

    I have a SL70 that looks the same, and has M5 on the bottom...but no L on top.
     
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