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Thread: Extra valve spring seat on exhaust side, ATC70

  1. #1
    Join Date
    Oct 2019
    Location
    Canada
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    99

    Extra valve spring seat on exhaust side, ATC70

    Just putting my engine back together. The parts diagram shows an extra inner valve spring seat on the exhaust side, item (13).

    https://www.babbittsonline.com/oempa...amshaft-valveo

    Can anybody confirm if this is correct? I don't remember an extra piece during disassembly, and I can't see why it's needed. To me, it looks like the caps which hold the valve stem seals, serve as the seat for the inner valve spring.

    Could it possibly be just a drawing error, old configuration, etc.?

    Thanks!

  2. #2
    Join Date
    May 2009
    Location
    S.E. Michigan
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    1,250
    So, I have an engine on the bench that I'd been meaning to strip the top end on... so I just went out and pulled the exhaust valve and took pics.

    Bottom line: the parts diagram is right, but those parts are kinda sneaky. The drawings make them all look so similar in size, but there is a difference in diameters.

    My engine is an 83, but I think it's the same as yours.

    So, #12 is the outer spring seat, and on my engine, that seat doesn't want to come off the head. I tried popping it out, but it wouldn't come out. This is for the larger outer spring to seat on. (no pics of this here, sorry)

    #13 and #8 at first seemed to be a single piece. However, with a small pick, I was able to separate the #13 piece (basically a washer with a flared inner diameter) off of the #8 seat. These are smaller in diameter than the #12 outer spring seat. They are smaller in diameter than the inner spring seat.

    Here are some pics:
    Inner spring with #13 and #8 all in assembled position
    Click image for larger version. 

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    Inner seat assembly removed from spring (#13 is on #8 and appears as one unit)
    Click image for larger version. 

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    A pick was used to pop #13 free of #8
    Click image for larger version. 

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    All three pieces separated
    Click image for larger version. 

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    - Frank

    1984 200ES Big Red
    1985 350X (x2)
    1986 350X
    1986 250SX
    1984 Auto-X
    1984 ATC70
    1985 ATC70

  3. #3
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Great info, thanks for checking. I guess I shall double check.

    Now, the story continues: I just took apart a cylinder head that I got with parts and a 1985 ATC70. The trike has a complete new aftermarket head on it, so I assume the extra head is the OEM from that trike. Pulled the valve springs on intake & exhaust sides, and BOTH have an inner valve spring seat (#13) installed.

    Checked the parts fiche from 1985 back to 1979; no changes in valvetrain.

    So..... Still leaning towards a drawing error. The springs are the same on both exhaust & intake, so why wouldn't Honda call up a (#13) seat on both sides?

    Wonderboy- did you happen to pull the springs on the intake side, and check to see if it has the same inner spring seat?
    Last edited by Baba Yaga; 07-16-2020 at 10:54 PM.

  4. #4
    Join Date
    Oct 2002
    Location
    Northeast
    --
    17,438
    I too find it odd that they'd only use that on one sides spring.

    If the springs were different from IN to EX, I get it, but they are identical...
    All our government does is distract us while they steal from us, misspend our tax $ and ruin our country

  5. #5
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Yep, and I checked the Honda FSM today; it shows an inner spring seat for both valves. That, and the head I disassembled which had a seat for both valves, leads me to believe that the parts diagram is incorrect.

    Click image for larger version. 

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  6. #6
    Join Date
    May 2009
    Location
    S.E. Michigan
    --
    1,250
    Sounds like you confirmed it is there on both sides, but for what it's worth, I'll pull the intake valve on my motor tomorrow and give you another reference point.
    - Frank

    1984 200ES Big Red
    1985 350X (x2)
    1986 350X
    1986 250SX
    1984 Auto-X
    1984 ATC70
    1985 ATC70

  7. #7
    Join Date
    Jun 2020
    Location
    John Fahey's sister's couch
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    53
    Quote Originally Posted by Baba Yaga View Post
    Great info, thanks for checking. I guess I shall double check.

    Now, the story continues: I just took apart a cylinder head that I got with parts and a 1985 ATC70. The trike has a complete new aftermarket head on it, so I assume the extra head is the OEM from that trike. Pulled the valve springs on intake & exhaust sides, and BOTH have an inner valve spring seat (#13) installed.

    Checked the parts fiche from 1985 back to 1979; no changes in valvetrain.

    So..... Still leaning towards a drawing error. The springs are the same on both exhaust & intake, so why wouldn't Honda call up a (#13) seat on both sides?

    Wonderboy- did you happen to pull the springs on the intake side, and check to see if it has the same inner spring seat?
    You just explained that the drawing is correct.

  8. #8
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Quote Originally Posted by fabiobriven View Post
    You just explained that the drawing is correct.
    Lol, no. The drawing in the Honda service manual (posted previously) shows a valve spring seat for both valves. The Honda parts fiche only shows it on the exhaust valve. One of them is incorrect, and I suspect it's the Honda parts fiche drawing.

  9. #9
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Quote Originally Posted by wonderboy View Post
    Sounds like you confirmed it is there on both sides, but for what it's worth, I'll pull the intake valve on my motor tomorrow and give you another reference point.
    Wonderboy, did you ever get a chance to check?
    Engine is back together and runs nicely.

  10. #10
    Join Date
    May 2009
    Location
    S.E. Michigan
    --
    1,250
    I'll try to get out to the garage today and check. It's been so darn hot lately... inside projects have been preferred.
    - Frank

    1984 200ES Big Red
    1985 350X (x2)
    1986 350X
    1986 250SX
    1984 Auto-X
    1984 ATC70
    1985 ATC70

  11. #11
    Join Date
    May 2009
    Location
    S.E. Michigan
    --
    1,250
    Confirmed that the intake is identical to the exhaust side. The extra little washer is present on the inner spring seat, just like the exhaust.
    - Frank

    1984 200ES Big Red
    1985 350X (x2)
    1986 350X
    1986 250SX
    1984 Auto-X
    1984 ATC70
    1985 ATC70

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